Auto merge of #23748 - saschanaz:default-dict, r=Manishearth

Sync WebIDL.py with gecko

<!-- Please describe your changes on the following line: -->

The new change requires default dictionary value for optional dictionary-type arguments.

---
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- [ ] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23703

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- [x] There are tests for these changes

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106 files changed, 832 insertions, 319 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 9c40f21b496..797d0fdef66 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3969,7 +3969,7 @@ dependencies = [
 name = "script_plugins"
 version = "0.0.1"
 dependencies = [
- "weedle 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "weedle 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -5534,7 +5534,7 @@ dependencies = [
 
 [[package]]
 name = "weedle"
-version = "0.9.0"
+version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "nom 4.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -6180,7 +6180,7 @@ dependencies = [
 "checksum webrender_build 0.0.1 (git+https://github.com/jdm/webrender?branch=servo-hl)" = "<none>"
 "checksum webxr 0.0.1 (git+https://github.com/servo/webxr)" = "<none>"
 "checksum webxr-api 0.0.1 (git+https://github.com/servo/webxr)" = "<none>"
-"checksum weedle 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bcc44aa200daee8b1f3a004beaf16554369746f1b4486f0cf93b0caf8a3c2d1e"
+"checksum weedle 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3bb43f70885151e629e2a19ce9e50bd730fd436cfd4b666894c9ce4de9141164"
 "checksum which 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b57acb10231b9493c8472b20cb57317d0679a49e0bdbee44b3b803a6473af164"
 "checksum winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)" = "f10e386af2b13e47c89e7236a7a14a086791a2b88ebad6df9bf42040195cf770"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 114b403d077..98df7a8b51f 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -17,6 +17,7 @@ import functools
 from WebIDL import (
     BuiltinTypes,
     IDLBuiltinType,
+    IDLDefaultDictionaryValue,
     IDLEmptySequenceValue,
     IDLInterfaceMember,
     IDLNullableType,
@@ -678,13 +679,16 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             return None
 
         if isinstance(defaultValue, IDLNullValue):
-            assert type.nullable() or type.isDictionary()
+            assert type.nullable()
+            return nullValue
+        elif isinstance(defaultValue, IDLDefaultDictionaryValue):
+            assert type.isDictionary()
             return nullValue
         elif isinstance(defaultValue, IDLEmptySequenceValue):
             assert type.isSequence()
             return "Vec::new()"
 
-        raise TypeError("Can't handle non-null or non-empty sequence default value here")
+        raise TypeError("Can't handle non-null, non-empty sequence or non-empty dictionary default value here")
 
     # A helper function for wrapping up the template body for
     # possibly-nullable objecty stuff
@@ -747,17 +751,19 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             for memberType in type.unroll().flatMemberTypes
             if memberType.isDictionary()
         ]
-        if defaultValue and not isinstance(defaultValue, IDLNullValue):
+        if (defaultValue and
+                not isinstance(defaultValue, IDLNullValue) and
+                not isinstance(defaultValue, IDLDefaultDictionaryValue)):
             tag = defaultValue.type.tag()
             if tag is IDLType.Tags.bool:
                 default = "%s::Boolean(%s)" % (
                     union_native_type(type),
                     "true" if defaultValue.value else "false")
             else:
-                raise("We don't currently support default values that aren't null or boolean")
+                raise("We don't currently support default values that aren't null, boolean or default dictionary")
         elif dictionaries:
             if defaultValue:
-                assert isinstance(defaultValue, IDLNullValue)
+                assert isinstance(defaultValue, IDLDefaultDictionaryValue)
                 dictionary, = dictionaries
                 default = "%s::%s(%s::%s::empty())" % (
                     union_native_type(type),
diff --git a/components/script/dom/bindings/codegen/parser/WebIDL.py b/components/script/dom/bindings/codegen/parser/WebIDL.py
index df88cf120dd..e18b6e34a2c 100644
--- a/components/script/dom/bindings/codegen/parser/WebIDL.py
+++ b/components/script/dom/bindings/codegen/parser/WebIDL.py
@@ -1,16 +1,18 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 """ A WebIDL parser. """
 
+from __future__ import print_function
 from ply import lex, yacc
 import re
 import os
 import traceback
 import math
 import string
-from collections import defaultdict
+from collections import defaultdict, OrderedDict
+from itertools import chain
 
 # Machinery
 
@@ -40,32 +42,22 @@ def parseInt(literal):
     return value * sign
 
 
-# Magic for creating enums
-def M_add_class_attribs(attribs, start):
-    def foo(name, bases, dict_):
-        for v, k in enumerate(attribs):
-            dict_[k] = start + v
-        assert 'length' not in dict_
-        dict_['length'] = start + len(attribs)
-        return type(name, bases, dict_)
-    return foo
-
-
 def enum(*names, **kw):
-    if len(kw) == 1:
-        base = kw['base'].__class__
-        start = base.length
-    else:
-        assert len(kw) == 0
-        base = object
-        start = 0
-
-    class Foo(base):
-        __metaclass__ = M_add_class_attribs(names, start)
-
+    class Foo(object):
+        attrs = OrderedDict()
+        def __init__(self, names):
+            for v, k in enumerate(names):
+                self.attrs[k] = v
+        def __getattr__(self, attr):
+            if attr in self.attrs:
+                return self.attrs[attr]
+            raise AttributeError
         def __setattr__(self, name, value):  # this makes it read-only
             raise NotImplementedError
-    return Foo()
+
+    if "base" not in kw:
+        return Foo(names)
+    return Foo(chain(kw["base"].attrs.keys(), names))
 
 
 class WebIDLError(Exception):
@@ -482,9 +474,6 @@ class IDLExposureMixins():
     def isExposedOnMainThread(self):
         return self.isExposedInWindow()
 
-    def isExposedOffMainThread(self):
-        return len(self.exposureSet - {'Window', 'FakeTestPrimaryGlobal'}) > 0
-
     def isExposedInAnyWorker(self):
         return len(self.getWorkerExposureSet()) > 0
 
@@ -568,6 +557,9 @@ class IDLExternalInterface(IDLObjectWithIdentifier, IDLExposureMixins):
     def isNavigatorProperty(self):
         return False
 
+    def isSerializable(self):
+        return False
+
     def _getDependentObjects(self):
         return set()
 
@@ -704,6 +696,7 @@ class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
         # outputs the constructs in the order that namedConstructors enumerates
         # them.
         self.namedConstructors = list()
+        self.legacyWindowAliases = []
         self.implementedInterfaces = set()
         self._consequential = False
         self._isKnownNonPartial = False
@@ -774,6 +767,16 @@ class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
 
         IDLExposureMixins.finish(self, scope)
 
+        if len(self.legacyWindowAliases) > 0:
+            if not self.hasInterfaceObject():
+                raise WebIDLError("Interface %s unexpectedly has [LegacyWindowAlias] "
+                                  "and [NoInterfaceObject] together" % self.identifier.name,
+                                  [self.location])
+            if not self.isExposedInWindow():
+                raise WebIDLError("Interface %s has [LegacyWindowAlias] "
+                                  "but not exposed in Window" % self.identifier.name,
+                                  [self.location])
+
         # Now go ahead and merge in our partial interfaces.
         for partial in self._partialInterfaces:
             partial.finish(scope)
@@ -962,7 +965,6 @@ class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
         # self.members.  Sort our consequential interfaces by name
         # just so we have a consistent order.
         for iface in sorted(self.getConsequentialInterfaces(),
-                            cmp=cmp,
                             key=lambda x: x.identifier.name):
             # Flag the interface as being someone's consequential interface
             iface.setIsConsequentialInterfaceOf(self)
@@ -1325,6 +1327,7 @@ class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
                 for bindingAlias in member.bindingAliases:
                     checkDuplicateNames(member, bindingAlias, "BindingAlias")
 
+
         # Conditional exposure makes no sense for interfaces with no
         # interface object, unless they're navigator properties.
         # And SecureContext makes sense for interfaces with no interface object,
@@ -1640,6 +1643,11 @@ class IDLInterface(IDLInterfaceOrNamespace):
                         raise WebIDLError(str(identifier) + " must take no arguments",
                                           [attr.location])
 
+                if self.globalNames:
+                    raise WebIDLError("[%s] must not be specified together with "
+                                      "[Global]" % identifier,
+                                      [self.location, attr.location])
+
                 args = attr.args() if attr.hasArgs() else []
 
                 retType = IDLWrapperType(self.location, self)
@@ -1700,6 +1708,10 @@ class IDLInterface(IDLInterfaceOrNamespace):
                                       "an interface with inherited interfaces",
                                       [attr.location, self.location])
             elif identifier == "Global":
+                if self.ctor() or self.namedConstructors:
+                    raise WebIDLError("[Global] cannot be specified on an "
+                                      "interface with a constructor",
+                                      [attr.location, self.location]);
                 if attr.hasValue():
                     self.globalNames = [attr.value()]
                 elif attr.hasArgs():
@@ -1723,6 +1735,18 @@ class IDLInterface(IDLInterfaceOrNamespace):
                 self.parentScope.addIfaceGlobalNames(self.identifier.name,
                                                      [self.identifier.name])
                 self._isOnGlobalProtoChain = True
+            elif identifier == "LegacyWindowAlias":
+                if attr.hasValue():
+                    self.legacyWindowAliases = [attr.value()]
+                elif attr.hasArgs():
+                    self.legacyWindowAliases = attr.args()
+                else:
+                    raise WebIDLError("[%s] must either take an identifier "
+                                      "or take an identifier list" % identifier,
+                                      [attr.location])
+                for alias in self.legacyWindowAliases:
+                    unresolved = IDLUnresolvedIdentifier(attr.location, alias)
+                    IDLObjectWithIdentifier(attr.location, self.parentScope, unresolved)
             elif identifier == "SecureContext":
                 if not attr.noArguments():
                     raise WebIDLError("[%s] must take no arguments" % identifier,
@@ -1744,6 +1768,7 @@ class IDLInterface(IDLInterfaceOrNamespace):
                   identifier == "LegacyUnenumerableNamedProperties" or
                   identifier == "RunConstructorInCallerCompartment" or
                   identifier == "WantsEventListenerHooks" or
+                  identifier == "Serializable" or
                   identifier == "Abstract" or
                   identifier == "Inline"):
                 # Known extended attributes that do not take values
@@ -1770,6 +1795,19 @@ class IDLInterface(IDLInterfaceOrNamespace):
             attrlist = attr.listValue()
             self._extendedAttrDict[identifier] = attrlist if len(attrlist) else True
 
+    def validate(self):
+        IDLInterfaceOrNamespace.validate(self)
+        if self.parent and self.isSerializable() and not self.parent.isSerializable():
+            raise WebIDLError(
+                "Serializable interface inherits from non-serializable "
+                "interface.  Per spec, that means the object should not be "
+                "serializable, so chances are someone made a mistake here "
+                "somewhere.",
+                [self.location, self.parent.location])
+
+    def isSerializable(self):
+        return self.getExtendedAttribute("Serializable")
+
 
 class IDLNamespace(IDLInterfaceOrNamespace):
     def __init__(self, location, parentScope, name, members, isKnownNonPartial):
@@ -1805,7 +1843,9 @@ class IDLNamespace(IDLInterfaceOrNamespace):
                 if not attr.noArguments():
                     raise WebIDLError("[%s] must not have arguments" % identifier,
                                       [attr.location])
-            elif identifier == "Pref" or identifier == "Func":
+            elif (identifier == "Pref" or
+                  identifier == "HeaderFile" or
+                  identifier == "Func"):
                 # Known extended attributes that take a string value
                 if not attr.hasValue():
                     raise WebIDLError("[%s] must have a value" % identifier,
@@ -1818,6 +1858,9 @@ class IDLNamespace(IDLInterfaceOrNamespace):
             attrlist = attr.listValue()
             self._extendedAttrDict[identifier] = attrlist if len(attrlist) else True
 
+    def isSerializable(self):
+        return False
+
 
 class IDLDictionary(IDLObjectWithScope):
     def __init__(self, location, parentScope, name, parent, members):
@@ -1877,7 +1920,7 @@ class IDLDictionary(IDLObjectWithScope):
                 assert member.type.isComplete()
 
         # Members of a dictionary are sorted in lexicographic order
-        self.members.sort(cmp=cmp, key=lambda x: x.identifier.name)
+        self.members.sort(key=lambda x: x.identifier.name)
 
         inheritedMembers = []
         ancestor = self.parent
@@ -2232,7 +2275,7 @@ class IDLUnresolvedType(IDLType):
 
         assert obj
         if obj.isType():
-            print obj
+            print(obj)
         assert not obj.isType()
         if obj.isTypedef():
             assert self.name.name == obj.identifier.name
@@ -3562,8 +3605,6 @@ class IDLNullValue(IDLObject):
     def coerceToType(self, type, location):
         if (not isinstance(type, IDLNullableType) and
             not (type.isUnion() and type.hasNullableType) and
-            not (type.isUnion() and type.hasDictionaryType()) and
-            not type.isDictionary() and
             not type.isAny()):
             raise WebIDLError("Cannot coerce null value to type %s." % type,
                               [location])
@@ -3612,6 +3653,35 @@ class IDLEmptySequenceValue(IDLObject):
         return set()
 
 
+class IDLDefaultDictionaryValue(IDLObject):
+    def __init__(self, location):
+        IDLObject.__init__(self, location)
+        self.type = None
+        self.value = None
+
+    def coerceToType(self, type, location):
+        if type.isUnion():
+            # We use the flat member types here, because if we have a nullable
+            # member type, or a nested union, we want the type the value
+            # actually coerces to, not the nullable or nested union type.
+            for subtype in type.unroll().flatMemberTypes:
+                try:
+                    return self.coerceToType(subtype, location)
+                except:
+                    pass
+
+        if not type.isDictionary():
+            raise WebIDLError("Cannot coerce default dictionary value to type %s." % type,
+                              [location])
+
+        defaultDictionaryValue = IDLDefaultDictionaryValue(self.location)
+        defaultDictionaryValue.type = type
+        return defaultDictionaryValue
+
+    def _getDependentObjects(self):
+        return set()
+
+
 class IDLUndefinedValue(IDLObject):
     def __init__(self, location):
         IDLObject.__init__(self, location)
@@ -3689,7 +3759,7 @@ class IDLInterfaceMember(IDLObjectWithIdentifier, IDLExposureMixins):
     def finish(self, scope):
         # We better be exposed _somewhere_.
         if (len(self._exposureGlobalNames) == 0):
-            print self.identifier.name
+            print(self.identifier.name)
         assert len(self._exposureGlobalNames) != 0
         IDLExposureMixins.finish(self, scope)
 
@@ -4577,7 +4647,9 @@ class IDLArgument(IDLObjectWithIdentifier):
             elif identifier == "TreatNonCallableAsNull":
                 self._allowTreatNonCallableAsNull = True
             elif (self.dictionaryMember and
-                  (identifier == "ChromeOnly" or identifier == "Func")):
+                  (identifier == "ChromeOnly" or
+                   identifier == "Func" or
+                   identifier == "Pref")):
                 if not self.optional:
                     raise WebIDLError("[%s] must not be used on a required "
                                       "dictionary member" % identifier,
@@ -4609,14 +4681,7 @@ class IDLArgument(IDLObjectWithIdentifier):
             assert not isinstance(type.name, IDLUnresolvedIdentifier)
             self.type = type
 
-        if ((self.type.isDictionary() or
-             self.type.isUnion() and self.type.unroll().hasDictionaryType()) and
-            self.optional and not self.defaultValue and not self.variadic and
-            not self.dictionaryMember):
-            # Default optional non-variadic dictionary arguments to null,
-            # for simplicity, so the codegen doesn't have to special-case this.
-            self.defaultValue = IDLNullValue(self.location)
-        elif self.type.isAny():
+        if self.type.isAny():
             assert (self.defaultValue is None or
                     isinstance(self.defaultValue, IDLNullValue))
             # optional 'any' values always have a default value
@@ -4648,7 +4713,7 @@ class IDLArgument(IDLObjectWithIdentifier):
 
 
 class IDLCallback(IDLObjectWithScope):
-    def __init__(self, location, parentScope, identifier, returnType, arguments):
+    def __init__(self, location, parentScope, identifier, returnType, arguments, isConstructor):
         assert isinstance(returnType, IDLType)
 
         self._returnType = returnType
@@ -4663,10 +4728,15 @@ class IDLCallback(IDLObjectWithScope):
 
         self._treatNonCallableAsNull = False
         self._treatNonObjectAsNull = False
+        self._isRunScriptBoundary = False
+        self._isConstructor = isConstructor
 
     def isCallback(self):
         return True
 
+    def isConstructor(self):
+        return self._isConstructor
+
     def signatures(self):
         return [(self._returnType, self._arguments)]
 
@@ -4699,7 +4769,16 @@ class IDLCallback(IDLObjectWithScope):
             if attr.identifier() == "TreatNonCallableAsNull":
                 self._treatNonCallableAsNull = True
             elif attr.identifier() == "TreatNonObjectAsNull":
+                if self._isConstructor:
+                    raise WebIDLError("[TreatNonObjectAsNull] is not supported "
+                                      "on constructors", [self.location])
                 self._treatNonObjectAsNull = True
+            elif attr.identifier() == "MOZ_CAN_RUN_SCRIPT_BOUNDARY":
+                if self._isConstructor:
+                    raise WebIDLError("[MOZ_CAN_RUN_SCRIPT_BOUNDARY] is not "
+                                      "permitted on constructors",
+                                      [self.location])
+                self._isRunScriptBoundary = True
             else:
                 unhandledAttrs.append(attr)
         if self._treatNonCallableAsNull and self._treatNonObjectAsNull:
@@ -4711,6 +4790,9 @@ class IDLCallback(IDLObjectWithScope):
     def _getDependentObjects(self):
         return set([self._returnType] + self._arguments)
 
+    def isRunScriptBoundary(self):
+        return self._isRunScriptBoundary;
+
 
 class IDLCallbackType(IDLType):
     def __init__(self, location, callback):
@@ -4757,6 +4839,9 @@ class IDLMethodOverload:
         deps.add(self.returnType)
         return deps
 
+    def includesRestrictedFloatArgument(self):
+        return any(arg.type.includesRestrictedFloat() for arg in self.arguments)
+
 
 class IDLMethod(IDLInterfaceMember, IDLScope):
 
@@ -4928,10 +5013,25 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
     def addOverload(self, method):
         assert len(method._overloads) == 1
 
-        if self._extendedAttrDict != method ._extendedAttrDict:
-            raise WebIDLError("Extended attributes differ on different "
-                              "overloads of %s" % method.identifier,
-                              [self.location, method.location])
+        if self._extendedAttrDict != method._extendedAttrDict:
+            extendedAttrDiff = set(self._extendedAttrDict.keys()) ^ set(method._extendedAttrDict.keys())
+
+            if extendedAttrDiff == { "LenientFloat" }:
+                if "LenientFloat" not in self._extendedAttrDict:
+                    for overload in self._overloads:
+                        if overload.includesRestrictedFloatArgument():
+                            raise WebIDLError("Restricted float behavior differs on different "
+                                              "overloads of %s" % method.identifier,
+                                              [overload.location, method.location])
+                    self._extendedAttrDict["LenientFloat"] = method._extendedAttrDict["LenientFloat"]
+                elif method._overloads[0].includesRestrictedFloatArgument():
+                    raise WebIDLError("Restricted float behavior differs on different "
+                                      "overloads of %s" % method.identifier,
+                                      [self.location, method.location])
+            else:
+                raise WebIDLError("Extended attributes differ on different "
+                                "overloads of %s" % method.identifier,
+                                [self.location, method.location])
 
         self._overloads.extend(method._overloads)
 
@@ -5039,6 +5139,15 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                                           "must be optional",
                                           [argument.location])
 
+                    if (not argument.defaultValue and
+                        all(arg.optional for arg in arguments[idx+1:])):
+                        raise WebIDLError("Dictionary argument without any "
+                                          "required fields or union argument "
+                                          "containing such dictionary not "
+                                          "followed by a required argument "
+                                          "must have a default value",
+                                          [argument.location])
+
                     # An argument cannot be a Nullable Dictionary
                     if argument.type.nullable():
                         raise WebIDLError("An argument cannot be a nullable "
@@ -5162,12 +5271,12 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                               [attr.location, self.location])
         elif identifier == "LenientFloat":
             # This is called before we've done overload resolution
-            assert len(self.signatures()) == 1
-            sig = self.signatures()[0]
-            if not sig[0].isVoid():
+            overloads = self._overloads
+            assert len(overloads) == 1
+            if not overloads[0].returnType.isVoid():
                 raise WebIDLError("[LenientFloat] used on a non-void method",
                                   [attr.location, self.location])
-            if not any(arg.type.includesRestrictedFloat() for arg in sig[1]):
+            if not overloads[0].includesRestrictedFloatArgument():
                 raise WebIDLError("[LenientFloat] used on an operation with no "
                                   "restricted float type arguments",
                                   [attr.location, self.location])
@@ -5238,7 +5347,7 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
             if self.signatures()[0][0] != BuiltinTypes[IDLBuiltinType.Types.object]:
                 raise WebIDLError("The return type of the default toJSON "
                                   "operation must be 'object'",
-                                  [attr.location, self.location]);
+                                  [attr.location, self.location])
         elif (identifier == "Throws" or
               identifier == "CanOOM" or
               identifier == "NewObject" or
@@ -5251,7 +5360,8 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
               identifier == "NeedsSubjectPrincipal" or
               identifier == "NeedsCallerType" or
               identifier == "StaticClassOverride" or
-              identifier == "NonEnumerable"):
+              identifier == "NonEnumerable" or
+              identifier == "Unexposed"):
             # Known attributes that we don't need to do anything with here
             pass
         else:
@@ -5478,6 +5588,7 @@ class Tokenizer(object):
         "iterable": "ITERABLE",
         "namespace": "NAMESPACE",
         "ReadableStream": "READABLESTREAM",
+        "constructor": "CONSTRUCTOR",
         }
 
     tokens.extend(keywords.values())
@@ -5604,6 +5715,7 @@ class Parser(Tokenizer):
     def p_CallbackRestOrInterface(self, p):
         """
             CallbackRestOrInterface : CallbackRest
+                                    | CallbackConstructorRest
                                     | Interface
         """
         assert p[1]
@@ -5637,7 +5749,7 @@ class Parser(Tokenizer):
                                       [location, existingObj.location])
                 existingObj.setNonPartial(*nonPartialArgs)
                 return existingObj
-        except Exception, ex:
+        except Exception as ex:
             if isinstance(ex, WebIDLError):
                 raise ex
             pass
@@ -5675,7 +5787,7 @@ class Parser(Tokenizer):
                                       "%s and %s" % (identifier.name, p[0]),
                                       [location, p[0].location])
                 return
-        except Exception, ex:
+        except Exception as ex:
             if isinstance(ex, WebIDLError):
                 raise ex
             pass
@@ -5739,7 +5851,7 @@ class Parser(Tokenizer):
                                       "non-%s object" %
                                       (prettyname, prettyname),
                                       [location, nonPartialObject.location])
-        except Exception, ex:
+        except Exception as ex:
             if isinstance(ex, WebIDLError):
                 raise ex
             pass
@@ -5905,12 +6017,23 @@ class Parser(Tokenizer):
         """
             DefaultValue : ConstValue
                          | LBRACKET RBRACKET
+                         | LBRACE RBRACE
         """
         if len(p) == 2:
             p[0] = p[1]
         else:
-            assert len(p) == 3  # Must be []
-            p[0] = IDLEmptySequenceValue(self.getLocation(p, 1))
+            assert len(p) == 3  # Must be [] or {}
+            if p[1] == "[":
+                p[0] = IDLEmptySequenceValue(self.getLocation(p, 1))
+            else:
+                assert p[1] == "{"
+                p[0] = IDLDefaultDictionaryValue(self.getLocation(p, 1))
+
+    def p_DefaultValueNull(self, p):
+        """
+            DefaultValue : NULL
+        """
+        p[0] = IDLNullValue(self.getLocation(p, 1))
 
     def p_Exception(self, p):
         """
@@ -5967,7 +6090,15 @@ class Parser(Tokenizer):
         """
         identifier = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
         p[0] = IDLCallback(self.getLocation(p, 1), self.globalScope(),
-                           identifier, p[3], p[5])
+                           identifier, p[3], p[5], isConstructor=False)
+
+    def p_CallbackConstructorRest(self, p):
+        """
+            CallbackConstructorRest : CONSTRUCTOR IDENTIFIER EQUALS ReturnType LPAREN ArgumentList RPAREN SEMICOLON
+        """
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        p[0] = IDLCallback(self.getLocation(p, 2), self.globalScope(),
+                           identifier, p[4], p[6], isConstructor=True)
 
     def p_ExceptionMembers(self, p):
         """
@@ -6041,12 +6172,6 @@ class Parser(Tokenizer):
         stringType = BuiltinTypes[IDLBuiltinType.Types.domstring]
         p[0] = IDLValue(location, stringType, p[1])
 
-    def p_ConstValueNull(self, p):
-        """
-            ConstValue : NULL
-        """
-        p[0] = IDLNullValue(self.getLocation(p, 1))
-
     def p_BooleanLiteralTrue(self, p):
         """
             BooleanLiteral : TRUE
@@ -6442,6 +6567,7 @@ class Parser(Tokenizer):
                          | ATTRIBUTE
                          | CALLBACK
                          | CONST
+                         | CONSTRUCTOR
                          | DELETER
                          | DICTIONARY
                          | ENUM
@@ -6566,6 +6692,7 @@ class Parser(Tokenizer):
                   | BYTE
                   | LEGACYCALLER
                   | CONST
+                  | CONSTRUCTOR
                   | DELETER
                   | DOUBLE
                   | EXCEPTION
@@ -6619,9 +6746,9 @@ class Parser(Tokenizer):
         """
         p[0] = p[2].withExtendedAttributes(p[1])
 
-    def p_SingleTypeNonAnyType(self, p):
+    def p_SingleTypeDistinguishableType(self, p):
         """
-            SingleType : NonAnyType
+            SingleType : DistinguishableType
         """
         p[0] = p[1]
 
@@ -6631,6 +6758,14 @@ class Parser(Tokenizer):
         """
         p[0] = BuiltinTypes[IDLBuiltinType.Types.any]
 
+    # Note: Promise<void> is allowed, so we want to parametrize on ReturnType,
+    # not Type.  Promise types can't be null, hence no "Null" in there.
+    def p_SingleTypePromiseType(self, p):
+        """
+            SingleType : PROMISE LT ReturnType GT
+        """
+        p[0] = IDLPromiseType(self.getLocation(p, 1), p[3])
+
     def p_UnionType(self, p):
         """
             UnionType : LPAREN UnionMemberType OR UnionMemberType UnionMemberTypes RPAREN
@@ -6639,9 +6774,9 @@ class Parser(Tokenizer):
         types.extend(p[5])
         p[0] = IDLUnionType(self.getLocation(p, 1), types)
 
-    def p_UnionMemberTypeNonAnyType(self, p):
+    def p_UnionMemberTypeDistinguishableType(self, p):
         """
-            UnionMemberType : ExtendedAttributeList NonAnyType
+            UnionMemberType : ExtendedAttributeList DistinguishableType
         """
         p[0] = p[2].withExtendedAttributes(p[1])
 
@@ -6664,13 +6799,13 @@ class Parser(Tokenizer):
         """
         p[0] = []
 
-    def p_NonAnyType(self, p):
+    def p_DistinguishableType(self, p):
         """
-            NonAnyType : PrimitiveType Null
-                       | ARRAYBUFFER Null
-                       | SHAREDARRAYBUFFER Null
-                       | READABLESTREAM Null
-                       | OBJECT Null
+            DistinguishableType : PrimitiveType Null
+                                | ARRAYBUFFER Null
+                                | SHAREDARRAYBUFFER Null
+                                | READABLESTREAM Null
+                                | OBJECT Null
         """
         if p[1] == "object":
             type = BuiltinTypes[IDLBuiltinType.Types.object]
@@ -6685,40 +6820,32 @@ class Parser(Tokenizer):
 
         p[0] = self.handleNullable(type, p[2])
 
-    def p_NonAnyTypeStringType(self, p):
+    def p_DistinguishableTypeStringType(self, p):
         """
-            NonAnyType : StringType Null
+            DistinguishableType : StringType Null
         """
         p[0] = self.handleNullable(p[1], p[2])
 
-    def p_NonAnyTypeSequenceType(self, p):
+    def p_DistinguishableTypeSequenceType(self, p):
         """
-            NonAnyType : SEQUENCE LT TypeWithExtendedAttributes GT Null
+            DistinguishableType : SEQUENCE LT TypeWithExtendedAttributes GT Null
         """
         innerType = p[3]
         type = IDLSequenceType(self.getLocation(p, 1), innerType)
         p[0] = self.handleNullable(type, p[5])
 
-    # Note: Promise<void> is allowed, so we want to parametrize on ReturnType,
-    # not Type.  Promise types can't be null, hence no "Null" in there.
-    def p_NonAnyTypePromiseType(self, p):
+    def p_DistinguishableTypeRecordType(self, p):
         """
-            NonAnyType : PROMISE LT ReturnType GT
-        """
-        p[0] = IDLPromiseType(self.getLocation(p, 1), p[3])
-
-    def p_NonAnyTypeRecordType(self, p):
-        """
-            NonAnyType : RECORD LT StringType COMMA TypeWithExtendedAttributes GT Null
+            DistinguishableType : RECORD LT StringType COMMA TypeWithExtendedAttributes GT Null
         """
         keyType = p[3]
         valueType = p[5]
         type = IDLRecordType(self.getLocation(p, 1), keyType, valueType)
         p[0] = self.handleNullable(type, p[7])
 
-    def p_NonAnyTypeScopedName(self, p):
+    def p_DistinguishableTypeScopedName(self, p):
         """
-            NonAnyType : ScopedName Null
+            DistinguishableType : ScopedName Null
         """
         assert isinstance(p[1], IDLUnresolvedIdentifier)
 
@@ -6748,28 +6875,26 @@ class Parser(Tokenizer):
         type = IDLUnresolvedType(self.getLocation(p, 1), p[1])
         p[0] = self.handleNullable(type, p[2])
 
-    def p_NonAnyTypeDate(self, p):
+    def p_DistinguishableTypeDate(self, p):
         """
-            NonAnyType : DATE Null
+            DistinguishableType : DATE Null
         """
         p[0] = self.handleNullable(BuiltinTypes[IDLBuiltinType.Types.date],
                                    p[2])
 
     def p_ConstType(self, p):
         """
-            ConstType : PrimitiveType Null
+            ConstType : PrimitiveType
         """
-        type = BuiltinTypes[p[1]]
-        p[0] = self.handleNullable(type, p[2])
+        p[0] = BuiltinTypes[p[1]]
 
     def p_ConstTypeIdentifier(self, p):
         """
-            ConstType : IDENTIFIER Null
+            ConstType : IDENTIFIER
         """
         identifier = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
 
-        type = IDLUnresolvedType(self.getLocation(p, 1), identifier)
-        p[0] = self.handleNullable(type, p[2])
+        p[0] = IDLUnresolvedType(self.getLocation(p, 1), identifier)
 
     def p_PrimitiveTypeUint(self, p):
         """
@@ -7040,8 +7165,8 @@ class Parser(Tokenizer):
     def _installBuiltins(self, scope):
         assert isinstance(scope, IDLScope)
 
-        # xrange omits the last value.
-        for x in xrange(IDLBuiltinType.Types.ArrayBuffer, IDLBuiltinType.Types.Float64Array + 1):
+        # range omits the last value.
+        for x in range(IDLBuiltinType.Types.ArrayBuffer, IDLBuiltinType.Types.Float64Array + 1):
             builtin = BuiltinTypes[x]
             name = builtin.name
             typedef = IDLTypedef(BuiltinLocation("<builtin type>"), scope, builtin, name)
@@ -7185,14 +7310,14 @@ def main():
             f = open(fullPath, 'rb')
             lines = f.readlines()
             f.close()
-            print fullPath
+            print(fullPath)
             parser.parse(''.join(lines), fullPath)
         parser.finish()
-    except WebIDLError, e:
+    except WebIDLError as e:
         if options.verbose_errors:
             traceback.print_exc()
         else:
-            print e
+            print(e)
 
 if __name__ == '__main__':
     main()
diff --git a/components/script/dom/bindings/codegen/parser/abstract.patch b/components/script/dom/bindings/codegen/parser/abstract.patch
index 8e6c272b2c5..e2db398a051 100644
--- a/components/script/dom/bindings/codegen/parser/abstract.patch
+++ b/components/script/dom/bindings/codegen/parser/abstract.patch
@@ -1,12 +1,12 @@
 --- WebIDL.py
 +++ WebIDL.py
-@@ -1786,7 +1786,8 @@ class IDLInterface(IDLInterfaceOrNamespace):
-                   identifier == "ProbablyShortLivingWrapper" or
+@@ -1768,7 +1768,8 @@ class IDLInterface(IDLInterfaceOrNamespace):
                    identifier == "LegacyUnenumerableNamedProperties" or
                    identifier == "RunConstructorInCallerCompartment" or
--                  identifier == "WantsEventListenerHooks"):
-+                  identifier == "WantsEventListenerHooks" or
+                   identifier == "WantsEventListenerHooks" or
+-                  identifier == "Serializable"):
++                  identifier == "Serializable" or
 +                  identifier == "Abstract"):
                  # Known extended attributes that do not take values
                  if not attr.noArguments():
-                     raise WebIDLError("[%s] must take no arguments" % identifier,
\ No newline at end of file
+                     raise WebIDLError("[%s] must take no arguments" % identifier,
diff --git a/components/script/dom/bindings/codegen/parser/callback-location.patch b/components/script/dom/bindings/codegen/parser/callback-location.patch
index 00b3b034396..b7a308df631 100644
--- a/components/script/dom/bindings/codegen/parser/callback-location.patch
+++ b/components/script/dom/bindings/codegen/parser/callback-location.patch
@@ -1,7 +1,7 @@
 --- WebIDL.py
 +++ WebIDL.py
-@@ -2275,7 +2275,7 @@ class IDLUnresolvedType(IDLType):
-             return typedefType.complete(scope)
+@@ -2283,7 +2283,7 @@ class IDLUnresolvedType(IDLType):
+             return typedefType.complete(scope).withExtendedAttributes(self.extraTypeAttributes)
          elif obj.isCallback() and not obj.isInterface():
              assert self.name.name == obj.identifier.name
 -            return IDLCallbackType(self.location, obj)
@@ -9,7 +9,7 @@
  
          name = self.name.resolve(scope, None)
          return IDLWrapperType(self.location, obj)
-@@ -6688,7 +6688,7 @@ class Parser(Tokenizer):
+@@ -6854,7 +6854,7 @@ class Parser(Tokenizer):
                      type = IDLTypedefType(self.getLocation(p, 1), obj.innerType,
                                            obj.identifier.name)
                  elif obj.isCallback() and not obj.isInterface():
diff --git a/components/script/dom/bindings/codegen/parser/debug.patch b/components/script/dom/bindings/codegen/parser/debug.patch
index 49cb962cbba..f9b3d940399 100644
--- a/components/script/dom/bindings/codegen/parser/debug.patch
+++ b/components/script/dom/bindings/codegen/parser/debug.patch
@@ -1,6 +1,6 @@
 --- WebIDL.py
 +++ WebIDL.py
-@@ -6959,7 +6959,8 @@ class Parser(Tokenizer):
+@@ -7123,7 +7123,8 @@ class Parser(Tokenizer):
              self.parser = yacc.yacc(module=self,
                                      outputdir=outputdir,
                                      tabmodule='webidlyacc',
diff --git a/components/script/dom/bindings/codegen/parser/inline.patch b/components/script/dom/bindings/codegen/parser/inline.patch
index e2b16f9b158..8337effd0f1 100644
--- a/components/script/dom/bindings/codegen/parser/inline.patch
+++ b/components/script/dom/bindings/codegen/parser/inline.patch
@@ -1,9 +1,9 @@
 --- WebIDL.py
 +++ WebIDL.py
-@@ -1787,7 +1787,8 @@ class IDLInterface(IDLInterfaceOrNamespace):
-                   identifier == "LegacyUnenumerableNamedProperties" or
+@@ -1769,7 +1769,8 @@ class IDLInterface(IDLInterfaceOrNamespace):
                    identifier == "RunConstructorInCallerCompartment" or
                    identifier == "WantsEventListenerHooks" or
+                   identifier == "Serializable" or
 -                  identifier == "Abstract"):
 +                  identifier == "Abstract" or
 +                  identifier == "Inline"):
diff --git a/components/script/dom/bindings/codegen/parser/pref-main-thread.patch b/components/script/dom/bindings/codegen/parser/pref-main-thread.patch
deleted file mode 100644
index a90d0593693..00000000000
--- a/components/script/dom/bindings/codegen/parser/pref-main-thread.patch
+++ /dev/null
@@ -1,27 +0,0 @@
---- WebIDL.py
-+++ WebIDL.py
-@@ -1362,12 +1362,6 @@ class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
-                 for bindingAlias in member.bindingAliases:
-                     checkDuplicateNames(member, bindingAlias, "BindingAlias")
- 
--
--        if self.getExtendedAttribute("Pref") and self.isExposedOffMainThread():
--            raise WebIDLError("[Pref] used on an interface that is not "
--                              "main-thread-only",
--                              [self.location])
--
-         # Conditional exposure makes no sense for interfaces with no
-         # interface object, unless they're navigator properties.
-         # And SecureContext makes sense for interfaces with no interface object,
-@@ -3619,11 +3613,6 @@ class IDLInterfaceMember(IDLObjectWithIdentifier, IDLExposureMixins):
-         IDLExposureMixins.finish(self, scope)
- 
-     def validate(self):
--        if self.getExtendedAttribute("Pref") and self.isExposedOffMainThread():
--            raise WebIDLError("[Pref] used on an interface member that is not "
--                              "main-thread-only",
--                              [self.location])
--
-         if self.isAttr() or self.isMethod():
-             if self.affects == "Everything" and self.dependsOn != "Everything":
-                 raise WebIDLError("Interface member is flagged as affecting "
diff --git a/components/script/dom/bindings/codegen/parser/runtests.py b/components/script/dom/bindings/codegen/parser/runtests.py
index 10dbc3292f7..0599bf55fec 100644
--- a/components/script/dom/bindings/codegen/parser/runtests.py
+++ b/components/script/dom/bindings/codegen/parser/runtests.py
@@ -62,7 +62,7 @@ def run_tests(tests, verbose):
         harness.start()
         try:
             _test.WebIDLTest.__call__(WebIDL.Parser(), harness)
-        except Exception, ex:
+        except Exception as ex:
             print("TEST-UNEXPECTED-FAIL | Unhandled exception in test %s: %s" % (testpath, ex))
             traceback.print_exc()
         finally:
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_attr.py b/components/script/dom/bindings/codegen/parser/tests/test_attr.py
index ad7aabc1918..35f680aaa82 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_attr.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_attr.py
@@ -133,7 +133,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should not allow [SetterThrows] on readonly attributes")
 
@@ -146,7 +146,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should spell [Throws] correctly")
 
@@ -159,7 +159,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should not allow [SameObject] on attributes not of interface type")
 
@@ -172,6 +172,6 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(not threw, "Should allow [SameObject] on attributes of interface type")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_callback.py b/components/script/dom/bindings/codegen/parser/tests/test_callback.py
index 4dfda1c3c76..c304d085ce5 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_callback.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_callback.py
@@ -32,3 +32,6 @@ def WebIDLTest(parser, harness):
     harness.ok(not isinstance(t, WebIDL.IDLWrapperType), "Attr has the right type")
     harness.ok(isinstance(t, WebIDL.IDLNullableType), "Attr has the right type")
     harness.ok(t.isCallback(), "Attr has the right type")
+
+    callback = results[1]
+    harness.ok(not callback.isConstructor(), "callback is not constructor")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_callback_constructor.py b/components/script/dom/bindings/codegen/parser/tests/test_callback_constructor.py
new file mode 100644
index 00000000000..4999deef623
--- /dev/null
+++ b/components/script/dom/bindings/codegen/parser/tests/test_callback_constructor.py
@@ -0,0 +1,63 @@
+import WebIDL
+
+def WebIDLTest(parser, harness):
+    parser.parse("""
+        interface TestCallbackConstructor {
+          attribute CallbackConstructorType? constructorAttribute;
+        };
+
+        callback constructor CallbackConstructorType = TestCallbackConstructor (unsigned long arg);
+    """)
+
+    results = parser.finish()
+
+    harness.ok(True, "TestCallbackConstructor interface parsed without error.")
+    harness.check(len(results), 2, "Should be two productions.")
+    iface = results[0]
+    harness.ok(isinstance(iface, WebIDL.IDLInterface),
+               "Should be an IDLInterface")
+    harness.check(iface.identifier.QName(), "::TestCallbackConstructor", "Interface has the right QName")
+    harness.check(iface.identifier.name, "TestCallbackConstructor", "Interface has the right name")
+    harness.check(len(iface.members), 1, "Expect %s members" % 1)
+
+    attr = iface.members[0]
+    harness.ok(isinstance(attr, WebIDL.IDLAttribute),
+               "Should be an IDLAttribute")
+    harness.ok(attr.isAttr(), "Should be an attribute")
+    harness.ok(not attr.isMethod(), "Attr is not an method")
+    harness.ok(not attr.isConst(), "Attr is not a const")
+    harness.check(attr.identifier.QName(), "::TestCallbackConstructor::constructorAttribute", "Attr has the right QName")
+    harness.check(attr.identifier.name, "constructorAttribute", "Attr has the right name")
+    t = attr.type
+    harness.ok(not isinstance(t, WebIDL.IDLWrapperType), "Attr has the right type")
+    harness.ok(isinstance(t, WebIDL.IDLNullableType), "Attr has the right type")
+    harness.ok(t.isCallback(), "Attr has the right type")
+
+    callback = results[1]
+    harness.ok(callback.isConstructor(), "Callback is constructor")
+
+    parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [TreatNonObjectAsNull]
+            callback constructor CallbackConstructorType = object ();
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should throw on TreatNonObjectAsNull callback constructors")
+
+    parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [MOZ_CAN_RUN_SCRIPT_BOUNDARY]
+            callback constructor CallbackConstructorType = object ();
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should not permit MOZ_CAN_RUN_SCRIPT_BOUNDARY callback constructors")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py b/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py
index dba16f53302..f726907c2fc 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py
@@ -38,7 +38,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, e:
+    except Exception as e:
         harness.ok(False, "Shouldn't have thrown for [CEReactions] used on writable attribute. %s" % e)
         threw = True
 
@@ -52,7 +52,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, e:
+    except Exception as e:
         harness.ok(False, "Shouldn't have thrown for [CEReactions] used on regular operations. %s" % e)
         threw = True
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_conditional_dictionary_member.py b/components/script/dom/bindings/codegen/parser/tests/test_conditional_dictionary_member.py
index 433b7e501a4..066300e8bb4 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_conditional_dictionary_member.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_conditional_dictionary_member.py
@@ -44,7 +44,7 @@ def WebIDLTest(parser, harness):
         };
       """)
       results = parser.finish()
-    except Exception, exception:
+    except Exception as exception:
         pass
 
     harness.ok(exception, "Should have thrown.")
@@ -70,7 +70,7 @@ def WebIDLTest(parser, harness):
         };
       """)
       results = parser.finish()
-    except Exception, exception:
+    except Exception as exception:
         pass
 
     harness.ok(exception, "Should have thrown (2).")
@@ -100,7 +100,7 @@ def WebIDLTest(parser, harness):
         };
       """)
       results = parser.finish()
-    except Exception, exception:
+    except Exception as exception:
         pass
 
     harness.ok(exception, "Should have thrown (3).")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_const.py b/components/script/dom/bindings/codegen/parser/tests/test_const.py
index 80b6fb0e9c8..918f284a226 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_const.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_const.py
@@ -12,9 +12,6 @@ expected = [
     ("::TestConsts::ll", "ll", "LongLong", -8),
     ("::TestConsts::t", "t", "Boolean", True),
     ("::TestConsts::f", "f", "Boolean", False),
-    ("::TestConsts::n", "n", "BooleanOrNull", None),
-    ("::TestConsts::nt", "nt", "BooleanOrNull", True),
-    ("::TestConsts::nf", "nf", "BooleanOrNull", False),
     ("::TestConsts::fl", "fl", "Float", 0.2),
     ("::TestConsts::db", "db", "Double", 0.2),
     ("::TestConsts::ufl", "ufl", "UnrestrictedFloat", 0.2),
@@ -39,9 +36,6 @@ def WebIDLTest(parser, harness):
           const long long ll = -010;
           const boolean t = true;
           const boolean f = false;
-          const boolean? n = null;
-          const boolean? nt = true;
-          const boolean? nf = false;
           const float fl = 0.2;
           const double db = 0.2;
           const unrestricted float ufl = 0.2;
@@ -78,3 +72,16 @@ def WebIDLTest(parser, harness):
                       "Const's value has the same type as the type")
         harness.check(const.value.value, value, "Const value has the right value.")
 
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface TestConsts {
+            const boolean? zero = 0;
+          };
+        """)
+        parser.finish()
+    except:
+        threw = True
+    harness.ok(threw, "Nullable types are not allowed for consts.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_constructor_global.py b/components/script/dom/bindings/codegen/parser/tests/test_constructor_global.py
new file mode 100644
index 00000000000..14d42caf09c
--- /dev/null
+++ b/components/script/dom/bindings/codegen/parser/tests/test_constructor_global.py
@@ -0,0 +1,87 @@
+def WebIDLTest(parser, harness):
+    threw = False
+    try:
+        parser.parse("""
+            [Constructor, Global]
+            interface TestConstructorGlobal {
+            };
+        """)
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global, Constructor]
+            interface TestConstructorGlobal {
+            };
+        """)
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global, NamedConstructor=FooBar]
+            interface TestNamedConstructorGlobal {
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [NamedConstructor=FooBar, Global]
+            interface TestNamedConstructorGlobal {
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global, HTMLConstructor]
+            interface TestHTMLConstructorGlobal {
+            };
+        """)
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [HTMLConstructor, Global]
+            interface TestHTMLConstructorGlobal {
+            };
+        """)
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_constructor_no_interface_object.py b/components/script/dom/bindings/codegen/parser/tests/test_constructor_no_interface_object.py
index 40708e7870e..e5413350a28 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_constructor_no_interface_object.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_constructor_no_interface_object.py
@@ -13,6 +13,7 @@ def WebIDLTest(parser, harness):
 
     harness.ok(threw, "Should have thrown.")
 
+    parser = parser.reset()
     threw = False
     try:
         parser.parse("""
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py b/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py
index 361b83ea52b..770f76b22f0 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py
@@ -174,6 +174,22 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
+              void doFoo(optional A arg);
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Trailing dictionary arg must have a default value")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            dictionary A {
+            };
+            interface X {
               void doFoo((A or DOMString) arg);
             };
         """)
@@ -191,6 +207,23 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
+              void doFoo(optional (A or DOMString) arg);
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw,
+               "Trailing union arg containing a dictionary must have a default value")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            dictionary A {
+            };
+            interface X {
               void doFoo(A arg1, optional long arg2);
             };
         """)
@@ -207,6 +240,22 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
+              void doFoo(optional A arg1, optional long arg2);
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Dictionary arg followed by optional arg must have default value")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            dictionary A {
+            };
+            interface X {
               void doFoo(A arg1, optional long arg2, long arg3);
             };
         """)
@@ -236,6 +285,24 @@ def WebIDLTest(parser, harness):
                "be optional")
 
     parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            dictionary A {
+            };
+            interface X {
+              void doFoo(optional (A or DOMString) arg1, optional long arg2);
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw,
+               "Union arg containing dictionary followed by optional arg must "
+               "have a default value")
+
+    parser = parser.reset()
     parser.parse("""
             dictionary A {
             };
@@ -326,7 +393,7 @@ def WebIDLTest(parser, harness):
         dictionary A {
         };
         interface X {
-          void doFoo(optional A arg);
+          void doFoo(optional A arg = {});
         };
     """)
     results = parser.finish()
@@ -337,13 +404,24 @@ def WebIDLTest(parser, harness):
         dictionary A {
         };
         interface X {
-          void doFoo(optional (A or DOMString) arg);
+          void doFoo(optional (A or DOMString) arg = {});
         };
     """)
     results = parser.finish()
     harness.ok(True, "Union arg containing a dictionary should actually parse")
 
     parser = parser.reset()
+    parser.parse("""
+        dictionary A {
+        };
+        interface X {
+          void doFoo(optional (A or DOMString) arg = "abc");
+        };
+    """)
+    results = parser.finish()
+    harness.ok(True, "Union arg containing a dictionary with string default should actually parse")
+
+    parser = parser.reset()
     threw = False
     try:
         parser.parse("""
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py b/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py
index 73a32b0acfb..e88c2b50d98 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py
@@ -3,13 +3,16 @@ def firstArgType(method):
 
 def WebIDLTest(parser, harness):
     parser.parse("""
+      // Give our dictionary a required member so we don't need to
+      // mess with optional and default values.
       dictionary Dict {
+        required long member;
       };
       callback interface Foo {
       };
       interface Bar {
         // Bit of a pain to get things that have dictionary types
-        void passDict(optional Dict arg);
+        void passDict(Dict arg);
         void passFoo(Foo arg);
         void passNullableUnion((object? or DOMString) arg);
         void passNullable(Foo? arg);
@@ -156,8 +159,8 @@ def WebIDLTest(parser, harness):
                  "AncestorInterface", "UnrelatedInterface",
                  "ImplementedInterface", "CallbackInterface",
                  "CallbackInterface?", "CallbackInterface2",
-                 "object", "Callback", "Callback2", "optional Dict",
-                 "optional Dict2", "sequence<long>", "sequence<short>",
+                 "object", "Callback", "Callback2", "Dict",
+                 "Dict2", "sequence<long>", "sequence<short>",
                  "record<DOMString, object>",
                  "record<USVString, Dict>",
                  "record<ByteString, long>",
@@ -165,7 +168,7 @@ def WebIDLTest(parser, harness):
                  "Promise<any>", "Promise<any>?",
                  "USVString", "ArrayBuffer", "ArrayBufferView", "SharedArrayBuffer",
                  "Uint8Array", "Uint16Array",
-                 "(long or Callback)", "optional (long or Dict)",
+                 "(long or Callback)", "(long or Dict)",
     ]
     # When we can parse Date, we need to add it here.
     # XXXbz we can, and should really do that...
@@ -174,7 +177,7 @@ def WebIDLTest(parser, harness):
     def allBut(list1, list2):
         return [a for a in list1 if a not in list2 and
                 (a != "any" and a != "Promise<any>" and a != "Promise<any>?")]
-    unions = [ "(long or Callback)", "optional (long or Dict)" ]
+    unions = [ "(long or Callback)", "(long or Dict)" ]
     numerics = [ "long", "short", "long?", "short?" ]
     booleans = [ "boolean", "boolean?" ]
     primitives = numerics + booleans
@@ -189,7 +192,7 @@ def WebIDLTest(parser, harness):
     interfaces = [ "Interface", "Interface?", "AncestorInterface",
                    "UnrelatedInterface", "ImplementedInterface" ] + bufferSourceTypes + sharedBufferSourceTypes
     nullables = (["long?", "short?", "boolean?", "Interface?",
-                  "CallbackInterface?", "optional Dict", "optional Dict2",
+                  "CallbackInterface?", "Dict", "Dict2",
                   "Date?", "any", "Promise<any>?"] +
                  allBut(unions, [ "(long or Callback)" ]))
     dates = [ "Date", "Date?" ]
@@ -233,8 +236,8 @@ def WebIDLTest(parser, harness):
     setDistinguishable("object", nonObjects)
     setDistinguishable("Callback", nonUserObjects)
     setDistinguishable("Callback2", nonUserObjects)
-    setDistinguishable("optional Dict", allBut(nonUserObjects, nullables))
-    setDistinguishable("optional Dict2", allBut(nonUserObjects, nullables))
+    setDistinguishable("Dict", allBut(nonUserObjects, nullables))
+    setDistinguishable("Dict2", allBut(nonUserObjects, nullables))
     setDistinguishable("sequence<long>",
                        allBut(argTypes, sequences + ["object"]))
     setDistinguishable("sequence<short>",
@@ -254,7 +257,7 @@ def WebIDLTest(parser, harness):
     setDistinguishable("SharedArrayBuffer", allBut(argTypes, ["SharedArrayBuffer", "object"]))
     setDistinguishable("(long or Callback)",
                        allBut(nonUserObjects, numerics))
-    setDistinguishable("optional (long or Dict)",
+    setDistinguishable("(long or Dict)",
                        allBut(nonUserObjects, numerics + nullables))
 
     def areDistinguishable(type1, type2):
@@ -273,8 +276,10 @@ def WebIDLTest(parser, harness):
           callback interface CallbackInterface2 {};
           callback Callback = any();
           callback Callback2 = long(short arg);
-          dictionary Dict {};
-          dictionary Dict2 {};
+          // Give our dictionaries required members so we don't need to
+          // mess with optional and default values.
+          dictionary Dict { required long member; };
+          dictionary Dict2 { required long member; };
           interface TestInterface {%s
           };
         """
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_empty_sequence_default_value.py b/components/script/dom/bindings/codegen/parser/tests/test_empty_sequence_default_value.py
index 350ae72f022..a713266c88e 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_empty_sequence_default_value.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_empty_sequence_default_value.py
@@ -10,7 +10,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Constant cannot have [] as a default value")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_error_colno.py b/components/script/dom/bindings/codegen/parser/tests/test_error_colno.py
index ca0674aec04..7afd15513c6 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_error_colno.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_error_colno.py
@@ -8,7 +8,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse(input)
         results = parser.finish()
-    except WebIDL.WebIDLError, e:
+    except WebIDL.WebIDLError as e:
         threw = True
         lines = str(e).split('\n')
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_error_lineno.py b/components/script/dom/bindings/codegen/parser/tests/test_error_lineno.py
index f11222e7a4d..70bb1883682 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_error_lineno.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_error_lineno.py
@@ -14,7 +14,7 @@ interface ?"""
     try:
         parser.parse(input)
         results = parser.finish()
-    except WebIDL.WebIDLError, e:
+    except WebIDL.WebIDLError as e:
         threw = True
         lines = str(e).split('\n')
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_exposed_extended_attribute.py b/components/script/dom/bindings/codegen/parser/tests/test_exposed_extended_attribute.py
index 48957098bfe..a6c04e30caf 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_exposed_extended_attribute.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_exposed_extended_attribute.py
@@ -124,7 +124,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on invalid Exposed value on interface.")
@@ -140,7 +140,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on invalid Exposed value on attribute.")
@@ -156,7 +156,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on invalid Exposed value on operation.")
@@ -172,7 +172,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on invalid Exposed value on constant.")
@@ -192,7 +192,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on member exposed where its interface is not.")
@@ -216,7 +216,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
 
     harness.ok(threw, "Should have thrown on LHS of implements being exposed where RHS is not.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_float_types.py b/components/script/dom/bindings/codegen/parser/tests/test_float_types.py
index 718f09c114b..b7325cf9d26 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_float_types.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_float_types.py
@@ -68,7 +68,7 @@ def WebIDLTest(parser, harness):
               long m(float arg);
             };
         """)
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "[LenientFloat] only allowed on void methods")
 
@@ -81,7 +81,7 @@ def WebIDLTest(parser, harness):
               void m(unrestricted float arg);
             };
         """)
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "[LenientFloat] only allowed on methods with unrestricted float args")
 
@@ -94,7 +94,7 @@ def WebIDLTest(parser, harness):
               void m(sequence<unrestricted float> arg);
             };
         """)
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "[LenientFloat] only allowed on methods with unrestricted float args (2)")
 
@@ -107,7 +107,7 @@ def WebIDLTest(parser, harness):
               void m((unrestricted float or FloatTypes) arg);
             };
         """)
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "[LenientFloat] only allowed on methods with unrestricted float args (3)")
 
@@ -120,6 +120,6 @@ def WebIDLTest(parser, harness):
               readonly attribute float foo;
             };
         """)
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "[LenientFloat] only allowed on writable attributes")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_identifier_conflict.py b/components/script/dom/bindings/codegen/parser/tests/test_identifier_conflict.py
index b510a30c044..0e9a6654aa7 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_identifier_conflict.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_identifier_conflict.py
@@ -9,7 +9,7 @@ def WebIDLTest(parser, harness):
         """)
         results = parser.finish()
         harness.ok(False, "Should fail to parse")
-    except Exception, e:
+    except Exception as e:
         harness.ok("Name collision" in e.message,
                    "Should have name collision for interface")
 
@@ -21,7 +21,7 @@ def WebIDLTest(parser, harness):
         """)
         results = parser.finish()
         harness.ok(False, "Should fail to parse")
-    except Exception, e:
+    except Exception as e:
         harness.ok("Name collision" in e.message,
                    "Should have name collision for dictionary")
 
@@ -33,7 +33,7 @@ def WebIDLTest(parser, harness):
         """)
         results = parser.finish()
         harness.ok(False, "Should fail to parse")
-    except Exception, e:
+    except Exception as e:
         harness.ok("Multiple unresolvable definitions" in e.message,
                    "Should have name collision for dictionary")
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_interface.py b/components/script/dom/bindings/codegen/parser/tests/test_interface.py
index a23243abe61..ea3e842907a 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_interface.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_interface.py
@@ -374,3 +374,89 @@ def WebIDLTest(parser, harness):
         threw = True
     harness.ok(threw,
                "Should not allow unknown extended attributes on interfaces")
+
+    parser = parser.reset()
+    parser.parse("""
+        [Global] interface Window {};
+        [Exposed=Window, LegacyWindowAlias=A]
+        interface B {};
+        [Exposed=Window, LegacyWindowAlias=(C, D)]
+        interface E {};
+    """);
+    results = parser.finish();
+    harness.check(results[1].legacyWindowAliases, ["A"],
+                  "Should support a single identifier")
+    harness.check(results[2].legacyWindowAliases, ["C", "D"],
+                  "Should support an identifier list")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [LegacyWindowAlias]
+            interface A {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+    harness.ok(threw,
+               "Should not allow [LegacyWindowAlias] with no value")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Exposed=Worker, LegacyWindowAlias=B]
+            interface A {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+    harness.ok(threw,
+               "Should not allow [LegacyWindowAlias] without Window exposure")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global] interface Window {};
+            interface A {};
+            [Exposed=Window, LegacyWindowAlias=A]
+            interface B {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+    harness.ok(threw,
+               "Should not allow [LegacyWindowAlias] to conflict with other identifiers")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global] interface Window {};
+            [Exposed=Window, LegacyWindowAlias=A]
+            interface B {};
+            interface A {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+    harness.ok(threw,
+               "Should not allow [LegacyWindowAlias] to conflict with other identifiers")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [Global] interface Window {};
+            [Exposed=Window, LegacyWindowAlias=A]
+            interface B {};
+            [Exposed=Window, LegacyWindowAlias=A]
+            interface C {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+    harness.ok(threw,
+               "Should not allow [LegacyWindowAlias] to conflict with other identifiers")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_interface_maplikesetlikeiterable.py b/components/script/dom/bindings/codegen/parser/tests/test_interface_maplikesetlikeiterable.py
index ee5d870c200..72aa7617b84 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_interface_maplikesetlikeiterable.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_interface_maplikesetlikeiterable.py
@@ -37,10 +37,10 @@ def WebIDLTest(parser, harness):
             p.finish()
             harness.ok(False,
                        prefix + " - Interface passed when should've failed")
-        except WebIDL.WebIDLError, e:
+        except WebIDL.WebIDLError as e:
             harness.ok(True,
                        prefix + " - Interface failed as expected")
-        except Exception, e:
+        except Exception as e:
             harness.ok(False,
                        prefix + " - Interface failed but not as a WebIDLError exception: %s" % e)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_lenientSetter.py b/components/script/dom/bindings/codegen/parser/tests/test_lenientSetter.py
index 50e9df658e9..78a9ffe9eaa 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_lenientSetter.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_lenientSetter.py
@@ -1,6 +1,6 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 def should_throw(parser, harness, message, code):
     parser = parser.reset();
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_method.py b/components/script/dom/bindings/codegen/parser/tests/test_method.py
index 29e6d6b25b7..88ee874386c 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_method.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_method.py
@@ -120,7 +120,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(not threw, "Should allow integer to float type corecion")
 
@@ -133,7 +133,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should not allow [GetterThrows] on methods")
 
@@ -146,7 +146,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should not allow [SetterThrows] on methods")
 
@@ -159,7 +159,7 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should spell [Throws] correctly on methods")
 
@@ -172,6 +172,85 @@ def WebIDLTest(parser, harness):
           };
         """)
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should not allow __noSuchMethod__ methods")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [Throws, LenientFloat]
+            void foo(float myFloat);
+            [Throws]
+            void foo();
+          };
+        """)
+        results = parser.finish()
+    except Exception as x:
+        threw = True
+    harness.ok(not threw, "Should allow LenientFloat to be only in a specific overload")
+
+    parser = parser.reset()
+    parser.parse("""
+      interface A {
+        [Throws]
+        void foo();
+        [Throws, LenientFloat]
+        void foo(float myFloat);
+      };
+    """)
+    results = parser.finish()
+    iface = results[0]
+    methods = iface.members
+    lenientFloat = methods[0].getExtendedAttribute("LenientFloat")
+    harness.ok(lenientFloat is not None, "LenientFloat in overloads must be added to the method")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [Throws, LenientFloat]
+            void foo(float myFloat);
+            [Throws]
+            void foo(float myFloat, float yourFloat);
+          };
+        """)
+        results = parser.finish()
+    except Exception as x:
+        threw = True
+    harness.ok(threw, "Should prevent overloads from getting different restricted float behavior")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [Throws]
+            void foo(float myFloat, float yourFloat);
+            [Throws, LenientFloat]
+            void foo(float myFloat);
+          };
+        """)
+        results = parser.finish()
+    except Exception as x:
+        threw = True
+    harness.ok(threw, "Should prevent overloads from getting different restricted float behavior (2)")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [Throws, LenientFloat]
+            void foo(float myFloat);
+            [Throws, LenientFloat]
+            void foo(short myShort);
+          };
+        """)
+        results = parser.finish()
+    except Exception as x:
+        threw = True
+    harness.ok(threw, "Should prevent overloads from getting redundant [LenientFloat]")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_namespace.py b/components/script/dom/bindings/codegen/parser/tests/test_namespace.py
index 74533a1770e..62edb270c63 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_namespace.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_namespace.py
@@ -70,7 +70,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -85,7 +85,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -104,7 +104,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -123,7 +123,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -142,7 +142,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -161,7 +161,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -180,7 +180,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -199,7 +199,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -218,6 +218,6 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_record.py b/components/script/dom/bindings/codegen/parser/tests/test_record.py
index c3fe29fa060..d50572caf07 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_record.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_record.py
@@ -33,7 +33,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown because record can't have void as value type.")
  
@@ -47,7 +47,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
     harness.ok(threw,
                "Should have thrown on dictionary containing itself via record.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_replaceable.py b/components/script/dom/bindings/codegen/parser/tests/test_replaceable.py
index 78b1bf7e60b..93ee42ed919 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_replaceable.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_replaceable.py
@@ -1,6 +1,6 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 def should_throw(parser, harness, message, code):
     parser = parser.reset();
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_typedef.py b/components/script/dom/bindings/codegen/parser/tests/test_typedef.py
index 8921985c5ca..b5fc1c68890 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_typedef.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_typedef.py
@@ -4,15 +4,15 @@ def WebIDLTest(parser, harness):
       typedef long? mynullablelong;
       interface Foo {
         const mylong X = 5;
-        const mynullablelong Y = 7;
-        const mynullablelong Z = null;
-        void foo(mylong arg);
+        void foo(optional mynullablelong arg = 7);
+        void bar(optional mynullablelong arg = null);
+        void baz(mylong arg);
       };
     """)
 
     results = parser.finish()
 
-    harness.check(results[2].members[1].type.name, "LongOrNull",
+    harness.check(results[2].members[1].signatures()[0][1][0].type.name, "LongOrNull",
                   "Should expand typedefs")
 
     parser = parser.reset()
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_unenumerable_own_properties.py b/components/script/dom/bindings/codegen/parser/tests/test_unenumerable_own_properties.py
index d017d5ce092..d28cc1ec052 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_unenumerable_own_properties.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_unenumerable_own_properties.py
@@ -24,7 +24,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -39,7 +39,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
 
@@ -59,6 +59,6 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception, x:
+    except Exception as x:
         threw = True
     harness.ok(threw, "Should have thrown.")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py b/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py
index 3787e8c6af1..44a168670ed 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py
@@ -111,7 +111,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
     harness.ok(threw,
                "Should have thrown when shadowing unforgeable attribute on "
@@ -130,7 +130,7 @@ def WebIDLTest(parser, harness):
         """)
 
         results = parser.finish()
-    except Exception,x:
+    except Exception as x:
         threw = True
     harness.ok(threw,
                "Should have thrown when shadowing unforgeable operation on "
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_union.py b/components/script/dom/bindings/codegen/parser/tests/test_union.py
index 9c4f2a56ab6..801314fd0bd 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_union.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_union.py
@@ -17,7 +17,7 @@ def combinations(iterable, r):
     n = len(pool)
     if r > n:
         return
-    indices = range(r)
+    indices = list(range(r))
     yield tuple(pool[i] for i in indices)
     while True:
         for i in reversed(range(r)):
diff --git a/components/script/dom/bindings/codegen/parser/update.sh b/components/script/dom/bindings/codegen/parser/update.sh
index 213aba6df89..fee9720ab2d 100755
--- a/components/script/dom/bindings/codegen/parser/update.sh
+++ b/components/script/dom/bindings/codegen/parser/update.sh
@@ -1,7 +1,6 @@
 wget https://hg.mozilla.org/mozilla-central/raw-file/tip/dom/bindings/parser/WebIDL.py -O WebIDL.py
 patch < abstract.patch
 patch < debug.patch
-patch < pref-main-thread.patch
 patch < callback-location.patch
 patch < union-typedef.patch
 patch < inline.patch
diff --git a/components/script/dom/webidls/AnalyserNode.webidl b/components/script/dom/webidls/AnalyserNode.webidl
index 6747cda0690..07826c16fab 100644
--- a/components/script/dom/webidls/AnalyserNode.webidl
+++ b/components/script/dom/webidls/AnalyserNode.webidl
@@ -14,7 +14,7 @@ dictionary AnalyserOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional AnalyserOptions options)]
+ Constructor (BaseAudioContext context, optional AnalyserOptions options = {})]
 interface AnalyserNode : AudioNode {
   void getFloatFrequencyData (Float32Array array);
   void getByteFrequencyData (Uint8Array array);
diff --git a/components/script/dom/webidls/AudioBufferSourceNode.webidl b/components/script/dom/webidls/AudioBufferSourceNode.webidl
index 929cdc05c1a..da1222a6935 100644
--- a/components/script/dom/webidls/AudioBufferSourceNode.webidl
+++ b/components/script/dom/webidls/AudioBufferSourceNode.webidl
@@ -16,7 +16,7 @@ dictionary AudioBufferSourceOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional AudioBufferSourceOptions options)]
+ Constructor (BaseAudioContext context, optional AudioBufferSourceOptions options = {})]
 interface AudioBufferSourceNode : AudioScheduledSourceNode {
   [Throws] attribute AudioBuffer? buffer;
   readonly attribute AudioParam playbackRate;
diff --git a/components/script/dom/webidls/AudioContext.webidl b/components/script/dom/webidls/AudioContext.webidl
index c47813d21e0..6acf7ec3e7c 100644
--- a/components/script/dom/webidls/AudioContext.webidl
+++ b/components/script/dom/webidls/AudioContext.webidl
@@ -23,7 +23,7 @@ dictionary AudioTimestamp {
 };
 
 [Exposed=Window,
- Constructor(optional AudioContextOptions contextOptions)]
+ Constructor(optional AudioContextOptions contextOptions = {})]
 interface AudioContext : BaseAudioContext {
   readonly attribute double baseLatency;
   readonly attribute double outputLatency;
diff --git a/components/script/dom/webidls/BiquadFilterNode.webidl b/components/script/dom/webidls/BiquadFilterNode.webidl
index e8ddaee1cac..d222e9a7297 100644
--- a/components/script/dom/webidls/BiquadFilterNode.webidl
+++ b/components/script/dom/webidls/BiquadFilterNode.webidl
@@ -26,7 +26,7 @@ dictionary BiquadFilterOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional BiquadFilterOptions options)]
+ Constructor (BaseAudioContext context, optional BiquadFilterOptions options = {})]
 interface BiquadFilterNode : AudioNode {
   attribute BiquadFilterType type;
   readonly attribute AudioParam frequency;
diff --git a/components/script/dom/webidls/Blob.webidl b/components/script/dom/webidls/Blob.webidl
index b06da6d2fae..d58c67a6398 100644
--- a/components/script/dom/webidls/Blob.webidl
+++ b/components/script/dom/webidls/Blob.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/FileAPI/#blob
 
 [Constructor(optional sequence<BlobPart> blobParts,
-  optional BlobPropertyBag options),
+  optional BlobPropertyBag options = {}),
  Exposed=(Window,Worker)]
 interface Blob {
 
diff --git a/components/script/dom/webidls/Bluetooth.webidl b/components/script/dom/webidls/Bluetooth.webidl
index c5ae3f8f26c..4491a296c41 100644
--- a/components/script/dom/webidls/Bluetooth.webidl
+++ b/components/script/dom/webidls/Bluetooth.webidl
@@ -34,7 +34,7 @@ interface Bluetooth : EventTarget {
   // [SecureContext, SameObject]
   // readonly attribute BluetoothDevice? referringDevice;
   [SecureContext]
-  Promise<BluetoothDevice> requestDevice(optional RequestDeviceOptions options);
+  Promise<BluetoothDevice> requestDevice(optional RequestDeviceOptions options = {});
 };
 
 // Bluetooth implements BluetoothDeviceEventHandlers;
diff --git a/components/script/dom/webidls/ChannelMergerNode.webidl b/components/script/dom/webidls/ChannelMergerNode.webidl
index f8345fe4512..33fc0e6ea67 100644
--- a/components/script/dom/webidls/ChannelMergerNode.webidl
+++ b/components/script/dom/webidls/ChannelMergerNode.webidl
@@ -11,6 +11,6 @@ dictionary ChannelMergerOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional ChannelMergerOptions options)]
+ Constructor (BaseAudioContext context, optional ChannelMergerOptions options = {})]
 interface ChannelMergerNode : AudioNode {
 };
diff --git a/components/script/dom/webidls/ChannelSplitterNode.webidl b/components/script/dom/webidls/ChannelSplitterNode.webidl
index 1056fce61bf..d776ac62ac3 100644
--- a/components/script/dom/webidls/ChannelSplitterNode.webidl
+++ b/components/script/dom/webidls/ChannelSplitterNode.webidl
@@ -11,6 +11,6 @@ dictionary ChannelSplitterOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional ChannelSplitterOptions options)]
+ Constructor (BaseAudioContext context, optional ChannelSplitterOptions options = {})]
 interface ChannelSplitterNode : AudioNode {
 };
diff --git a/components/script/dom/webidls/CloseEvent.webidl b/components/script/dom/webidls/CloseEvent.webidl
index f69d08c37a8..a689b337328 100644
--- a/components/script/dom/webidls/CloseEvent.webidl
+++ b/components/script/dom/webidls/CloseEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 //https://html.spec.whatwg.org/multipage/#the-closeevent-interfaces
-[Constructor(DOMString type, optional CloseEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional CloseEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface CloseEvent : Event {
   readonly attribute boolean wasClean;
   readonly attribute unsigned short code;
diff --git a/components/script/dom/webidls/CompositionEvent.webidl b/components/script/dom/webidls/CompositionEvent.webidl
index c018aa6deac..043873c9354 100644
--- a/components/script/dom/webidls/CompositionEvent.webidl
+++ b/components/script/dom/webidls/CompositionEvent.webidl
@@ -8,7 +8,7 @@
  */
 
 // https://w3c.github.io/uievents/#idl-compositionevent
-[Pref="dom.compositionevent.enabled", Constructor(DOMString type, optional CompositionEventInit eventInitDict)]
+[Pref="dom.compositionevent.enabled", Constructor(DOMString type, optional CompositionEventInit eventInitDict = {})]
 interface CompositionEvent : UIEvent {
   readonly attribute DOMString data;
 };
diff --git a/components/script/dom/webidls/CustomElementRegistry.webidl b/components/script/dom/webidls/CustomElementRegistry.webidl
index 1072eed0031..d2ebff0bdf0 100644
--- a/components/script/dom/webidls/CustomElementRegistry.webidl
+++ b/components/script/dom/webidls/CustomElementRegistry.webidl
@@ -6,7 +6,7 @@
 [Pref="dom.customelements.enabled"]
 interface CustomElementRegistry {
   [Throws, CEReactions]
-  void define(DOMString name, CustomElementConstructor constructor_, optional ElementDefinitionOptions options);
+  void define(DOMString name, CustomElementConstructor constructor_, optional ElementDefinitionOptions options = {});
 
   any get(DOMString name);
 
diff --git a/components/script/dom/webidls/CustomEvent.webidl b/components/script/dom/webidls/CustomEvent.webidl
index 2e77d67fe4b..5bede1513f2 100644
--- a/components/script/dom/webidls/CustomEvent.webidl
+++ b/components/script/dom/webidls/CustomEvent.webidl
@@ -13,7 +13,7 @@
  * http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
  */
 
-[Constructor(DOMString type, optional CustomEventInit eventInitDict),
+[Constructor(DOMString type, optional CustomEventInit eventInitDict = {}),
  Exposed=(Window,Worker)]
 interface CustomEvent : Event {
   readonly attribute any detail;
diff --git a/components/script/dom/webidls/DOMMatrix.webidl b/components/script/dom/webidls/DOMMatrix.webidl
index d617f20af99..ffaa720b7d9 100644
--- a/components/script/dom/webidls/DOMMatrix.webidl
+++ b/components/script/dom/webidls/DOMMatrix.webidl
@@ -14,7 +14,7 @@
  Exposed=(Window,Worker)]
 interface DOMMatrix : DOMMatrixReadOnly {
 
-    [NewObject, Throws] static DOMMatrix fromMatrix(optional DOMMatrixInit other);
+    [NewObject, Throws] static DOMMatrix fromMatrix(optional DOMMatrixInit other = {});
     [NewObject, Throws] static DOMMatrix fromFloat32Array(Float32Array array32);
     [NewObject, Throws] static DOMMatrix fromFloat64Array(Float64Array array64);
 
@@ -44,8 +44,8 @@ interface DOMMatrix : DOMMatrixReadOnly {
     inherit attribute unrestricted double m44;
 
     // Mutable transform methods
-    [Throws] DOMMatrix multiplySelf(optional DOMMatrixInit other);
-    [Throws] DOMMatrix preMultiplySelf(optional DOMMatrixInit other);
+    [Throws] DOMMatrix multiplySelf(optional DOMMatrixInit other = {});
+    [Throws] DOMMatrix preMultiplySelf(optional DOMMatrixInit other = {});
     DOMMatrix translateSelf(optional unrestricted double tx = 0,
                             optional unrestricted double ty = 0,
                             optional unrestricted double tz = 0);
diff --git a/components/script/dom/webidls/DOMMatrixReadOnly.webidl b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
index eb7051ba529..ea5d8caf8e5 100644
--- a/components/script/dom/webidls/DOMMatrixReadOnly.webidl
+++ b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
@@ -14,7 +14,7 @@
  Exposed=(Window,Worker)]
 interface DOMMatrixReadOnly {
 
-    [NewObject, Throws] static DOMMatrixReadOnly fromMatrix(optional DOMMatrixInit other);
+    [NewObject, Throws] static DOMMatrixReadOnly fromMatrix(optional DOMMatrixInit other = {});
     [NewObject, Throws] static DOMMatrixReadOnly fromFloat32Array(Float32Array array32);
     [NewObject, Throws] static DOMMatrixReadOnly fromFloat64Array(Float64Array array64);
 
@@ -73,12 +73,12 @@ interface DOMMatrixReadOnly {
                               optional unrestricted double angle = 0);
     DOMMatrix skewX(optional unrestricted double sx = 0);
     DOMMatrix skewY(optional unrestricted double sy = 0);
-    [Throws] DOMMatrix multiply(optional DOMMatrixInit other);
+    [Throws] DOMMatrix multiply(optional DOMMatrixInit other = {});
     DOMMatrix flipX();
     DOMMatrix flipY();
     DOMMatrix inverse();
 
-    DOMPoint            transformPoint(optional DOMPointInit point);
+    DOMPoint            transformPoint(optional DOMPointInit point = {});
     Float32Array        toFloat32Array();
     Float64Array        toFloat64Array();
 //                      stringifier;
diff --git a/components/script/dom/webidls/DOMPoint.webidl b/components/script/dom/webidls/DOMPoint.webidl
index 9f75a1c835f..34a355f6085 100644
--- a/components/script/dom/webidls/DOMPoint.webidl
+++ b/components/script/dom/webidls/DOMPoint.webidl
@@ -14,7 +14,7 @@
              optional unrestricted double z = 0, optional unrestricted double w = 1),
  Exposed=(Window,Worker)]
 interface DOMPoint : DOMPointReadOnly {
-    [NewObject] static DOMPoint fromPoint(optional DOMPointInit other = null);
+    [NewObject] static DOMPoint fromPoint(optional DOMPointInit other = {});
 
     inherit attribute unrestricted double x;
     inherit attribute unrestricted double y;
diff --git a/components/script/dom/webidls/DOMPointReadOnly.webidl b/components/script/dom/webidls/DOMPointReadOnly.webidl
index b6478f31337..23643179333 100644
--- a/components/script/dom/webidls/DOMPointReadOnly.webidl
+++ b/components/script/dom/webidls/DOMPointReadOnly.webidl
@@ -14,7 +14,7 @@
              optional unrestricted double z = 0, optional unrestricted double w = 1),
  Exposed=(Window,Worker)]
 interface DOMPointReadOnly {
-    [NewObject] static DOMPointReadOnly fromPoint(optional DOMPointInit other = null);
+    [NewObject] static DOMPointReadOnly fromPoint(optional DOMPointInit other = {});
 
     readonly attribute unrestricted double x;
     readonly attribute unrestricted double y;
diff --git a/components/script/dom/webidls/DOMQuad.webidl b/components/script/dom/webidls/DOMQuad.webidl
index 397118a88aa..8711dd44215 100644
--- a/components/script/dom/webidls/DOMQuad.webidl
+++ b/components/script/dom/webidls/DOMQuad.webidl
@@ -10,12 +10,12 @@
  * related or neighboring rights to this work.
  */
 
-[Constructor(optional DOMPointInit p1, optional DOMPointInit p2,
-             optional DOMPointInit p3, optional DOMPointInit p4),
+[Constructor(optional DOMPointInit p1 = {}, optional DOMPointInit p2 = {},
+             optional DOMPointInit p3 = {}, optional DOMPointInit p4 = {}),
  Exposed=(Window,Worker)]
 interface DOMQuad {
-    [NewObject] static DOMQuad fromRect(optional DOMRectInit other);
-    [NewObject] static DOMQuad fromQuad(optional DOMQuadInit other);
+    [NewObject] static DOMQuad fromRect(optional DOMRectInit other = {});
+    [NewObject] static DOMQuad fromQuad(optional DOMQuadInit other = {});
 
     [SameObject] readonly attribute DOMPoint p1;
     [SameObject] readonly attribute DOMPoint p2;
@@ -25,8 +25,8 @@ interface DOMQuad {
 };
 
 dictionary DOMQuadInit {
-    DOMPointInit p1 = null;
-    DOMPointInit p2 = null;
-    DOMPointInit p3 = null;
-    DOMPointInit p4 = null;
+    DOMPointInit p1 = {};
+    DOMPointInit p2 = {};
+    DOMPointInit p3 = {};
+    DOMPointInit p4 = {};
 };
diff --git a/components/script/dom/webidls/Document.webidl b/components/script/dom/webidls/Document.webidl
index 85c3362f42e..0127f8ecf98 100644
--- a/components/script/dom/webidls/Document.webidl
+++ b/components/script/dom/webidls/Document.webidl
@@ -33,9 +33,9 @@ interface Document : Node {
   HTMLCollection getElementsByClassName(DOMString classNames);
 
   [CEReactions, NewObject, Throws]
-  Element createElement(DOMString localName, optional ElementCreationOptions options);
+  Element createElement(DOMString localName, optional ElementCreationOptions options = {});
   [CEReactions, NewObject, Throws]
-  Element createElementNS(DOMString? namespace, DOMString qualifiedName, optional ElementCreationOptions options);
+  Element createElementNS(DOMString? namespace, DOMString qualifiedName, optional ElementCreationOptions options = {});
   [NewObject]
   DocumentFragment createDocumentFragment();
   [NewObject]
diff --git a/components/script/dom/webidls/Element.webidl b/components/script/dom/webidls/Element.webidl
index af14f81b373..f45dfe53f1a 100644
--- a/components/script/dom/webidls/Element.webidl
+++ b/components/script/dom/webidls/Element.webidl
@@ -91,12 +91,12 @@ partial interface Element {
   [NewObject]
   DOMRect getBoundingClientRect();
 
-  void scroll(optional ScrollToOptions options);
+  void scroll(optional ScrollToOptions options = {});
   void scroll(unrestricted double x, unrestricted double y);
 
-  void scrollTo(optional ScrollToOptions options);
+  void scrollTo(optional ScrollToOptions options = {});
   void scrollTo(unrestricted double x, unrestricted double y);
-  void scrollBy(optional ScrollToOptions options);
+  void scrollBy(optional ScrollToOptions options = {});
   void scrollBy(unrestricted double x, unrestricted double y);
   attribute unrestricted double scrollTop;
   attribute unrestricted double scrollLeft;
diff --git a/components/script/dom/webidls/ErrorEvent.webidl b/components/script/dom/webidls/ErrorEvent.webidl
index 9fb248e6095..165fbd35110 100644
--- a/components/script/dom/webidls/ErrorEvent.webidl
+++ b/components/script/dom/webidls/ErrorEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-errorevent-interface
 
-[Constructor(DOMString type, optional ErrorEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional ErrorEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface ErrorEvent : Event {
   readonly attribute DOMString message;
   readonly attribute DOMString filename;
diff --git a/components/script/dom/webidls/Event.webidl b/components/script/dom/webidls/Event.webidl
index 2bf103149d9..c688daedb2e 100644
--- a/components/script/dom/webidls/Event.webidl
+++ b/components/script/dom/webidls/Event.webidl
@@ -6,7 +6,7 @@
  * https://dom.spec.whatwg.org/#event
  */
 
-[Constructor(DOMString type, optional EventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional EventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface Event {
   [Pure]
   readonly attribute DOMString type;
diff --git a/components/script/dom/webidls/EventSource.webidl b/components/script/dom/webidls/EventSource.webidl
index d1c33a6c3fc..7784c97d4ca 100644
--- a/components/script/dom/webidls/EventSource.webidl
+++ b/components/script/dom/webidls/EventSource.webidl
@@ -6,7 +6,7 @@
  * https://html.spec.whatwg.org/multipage/#eventsource
  */
 
-[Constructor(DOMString url, optional EventSourceInit eventSourceInitDict),
+[Constructor(DOMString url, optional EventSourceInit eventSourceInitDict = {}),
  Exposed=(Window,Worker)]
 interface EventSource : EventTarget {
   readonly attribute DOMString url;
diff --git a/components/script/dom/webidls/EventTarget.webidl b/components/script/dom/webidls/EventTarget.webidl
index b0a6e77035e..283f86a806f 100644
--- a/components/script/dom/webidls/EventTarget.webidl
+++ b/components/script/dom/webidls/EventTarget.webidl
@@ -10,13 +10,13 @@ interface EventTarget {
   void addEventListener(
     DOMString type,
     EventListener? callback,
-    optional (AddEventListenerOptions or boolean) options
+    optional (AddEventListenerOptions or boolean) options = {}
   );
 
   void removeEventListener(
     DOMString type,
     EventListener? callback,
-    optional (EventListenerOptions or boolean) options
+    optional (EventListenerOptions or boolean) options = {}
   );
 
   [Throws]
diff --git a/components/script/dom/webidls/ExtendableEvent.webidl b/components/script/dom/webidls/ExtendableEvent.webidl
index 7dc2983fe74..5d6c4786c3f 100644
--- a/components/script/dom/webidls/ExtendableEvent.webidl
+++ b/components/script/dom/webidls/ExtendableEvent.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/ServiceWorker/#extendable-event
 
 [Constructor(DOMString type,
- optional ExtendableEventInit eventInitDict),
+ optional ExtendableEventInit eventInitDict = {}),
  Exposed=ServiceWorker,
  Pref="dom.serviceworker.enabled"]
 interface ExtendableEvent : Event {
diff --git a/components/script/dom/webidls/ExtendableMessageEvent.webidl b/components/script/dom/webidls/ExtendableMessageEvent.webidl
index 3b06fb08cd8..e934d06b50b 100644
--- a/components/script/dom/webidls/ExtendableMessageEvent.webidl
+++ b/components/script/dom/webidls/ExtendableMessageEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://w3c.github.io/ServiceWorker/#extendablemessage-event-section
 
-[Constructor(DOMString type, optional ExtendableMessageEventInit eventInitDict),
+[Constructor(DOMString type, optional ExtendableMessageEventInit eventInitDict = {}),
  Exposed=ServiceWorker,
  Pref="dom.serviceworker.enabled"]
 interface ExtendableMessageEvent : ExtendableEvent {
diff --git a/components/script/dom/webidls/Fetch.webidl b/components/script/dom/webidls/Fetch.webidl
index 3b424ba85b6..ad0907d7436 100644
--- a/components/script/dom/webidls/Fetch.webidl
+++ b/components/script/dom/webidls/Fetch.webidl
@@ -7,5 +7,5 @@
 [Exposed=(Window,Worker)]
 
 partial interface WindowOrWorkerGlobalScope {
-  [NewObject] Promise<Response> fetch(RequestInfo input, optional RequestInit init);
+  [NewObject] Promise<Response> fetch(RequestInfo input, optional RequestInit init = {});
 };
diff --git a/components/script/dom/webidls/File.webidl b/components/script/dom/webidls/File.webidl
index 00e1709ecc1..04e670723e4 100644
--- a/components/script/dom/webidls/File.webidl
+++ b/components/script/dom/webidls/File.webidl
@@ -6,7 +6,7 @@
 
 [Constructor(sequence<BlobPart> fileBits,
             DOMString fileName,
-            optional FilePropertyBag options),
+            optional FilePropertyBag options = {}),
  Exposed=(Window,Worker)]
 interface File : Blob {
   readonly attribute DOMString name;
diff --git a/components/script/dom/webidls/FocusEvent.webidl b/components/script/dom/webidls/FocusEvent.webidl
index 5371399228f..67dec33a952 100644
--- a/components/script/dom/webidls/FocusEvent.webidl
+++ b/components/script/dom/webidls/FocusEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-FocusEvent
-[Constructor(DOMString typeArg, optional FocusEventInit focusEventInitDict),
+[Constructor(DOMString typeArg, optional FocusEventInit focusEventInitDict = {}),
  Exposed=Window]
 interface FocusEvent : UIEvent {
   readonly attribute EventTarget?   relatedTarget;
diff --git a/components/script/dom/webidls/FormDataEvent.webidl b/components/script/dom/webidls/FormDataEvent.webidl
index d34f57b3a09..e478a33a729 100644
--- a/components/script/dom/webidls/FormDataEvent.webidl
+++ b/components/script/dom/webidls/FormDataEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-formdataevent-interface
 [Exposed=Window,
- Constructor(DOMString type, optional FormDataEventInit eventInitDict)]
+ Constructor(DOMString type, optional FormDataEventInit eventInitDict = {})]
 interface FormDataEvent : Event {
   readonly attribute FormData formData;
 };
diff --git a/components/script/dom/webidls/GainNode.webidl b/components/script/dom/webidls/GainNode.webidl
index 02bbbacb697..97b205e63e9 100644
--- a/components/script/dom/webidls/GainNode.webidl
+++ b/components/script/dom/webidls/GainNode.webidl
@@ -11,7 +11,7 @@ dictionary GainOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional GainOptions options)]
+ Constructor (BaseAudioContext context, optional GainOptions options = {})]
  interface GainNode : AudioNode {
    readonly attribute AudioParam gain;
  };
diff --git a/components/script/dom/webidls/HashChangeEvent.webidl b/components/script/dom/webidls/HashChangeEvent.webidl
index ec2065aa49e..e5049e75129 100644
--- a/components/script/dom/webidls/HashChangeEvent.webidl
+++ b/components/script/dom/webidls/HashChangeEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#hashchangeevent
-[Constructor(DOMString type, optional HashChangeEventInit eventInitDict),
+[Constructor(DOMString type, optional HashChangeEventInit eventInitDict = {}),
  Exposed=Window]
 interface HashChangeEvent : Event {
   readonly attribute USVString oldURL;
diff --git a/components/script/dom/webidls/InputEvent.webidl b/components/script/dom/webidls/InputEvent.webidl
index 23a62c06b2a..49fb9dc9695 100644
--- a/components/script/dom/webidls/InputEvent.webidl
+++ b/components/script/dom/webidls/InputEvent.webidl
@@ -8,7 +8,7 @@
  */
 
 // https://w3c.github.io/uievents/#idl-inputevent
-[Constructor(DOMString type, optional InputEventInit eventInitDict)]
+[Constructor(DOMString type, optional InputEventInit eventInitDict = {})]
 interface InputEvent : UIEvent {
   readonly attribute DOMString? data;
   readonly attribute boolean isComposing;
diff --git a/components/script/dom/webidls/KeyboardEvent.webidl b/components/script/dom/webidls/KeyboardEvent.webidl
index ed9350a9f29..f30265a87d8 100644
--- a/components/script/dom/webidls/KeyboardEvent.webidl
+++ b/components/script/dom/webidls/KeyboardEvent.webidl
@@ -7,7 +7,7 @@
  *
  */
 
-[Constructor(DOMString typeArg, optional KeyboardEventInit keyboardEventInitDict)]
+[Constructor(DOMString typeArg, optional KeyboardEventInit keyboardEventInitDict = {})]
 interface KeyboardEvent : UIEvent {
     // KeyLocationCode
     const unsigned long DOM_KEY_LOCATION_STANDARD = 0x00;
diff --git a/components/script/dom/webidls/MediaDevices.webidl b/components/script/dom/webidls/MediaDevices.webidl
index 866e1e964d0..0d9c3b9e98b 100644
--- a/components/script/dom/webidls/MediaDevices.webidl
+++ b/components/script/dom/webidls/MediaDevices.webidl
@@ -18,7 +18,7 @@ partial interface Navigator {
 
 partial interface MediaDevices {
     // MediaTrackSupportedConstraints getSupportedConstraints();
-    Promise<MediaStream> getUserMedia(optional MediaStreamConstraints constraints);
+    Promise<MediaStream> getUserMedia(optional MediaStreamConstraints constraints = {});
 };
 
 
diff --git a/components/script/dom/webidls/MediaQueryListEvent.webidl b/components/script/dom/webidls/MediaQueryListEvent.webidl
index 9f194a6feb6..36464230e1b 100644
--- a/components/script/dom/webidls/MediaQueryListEvent.webidl
+++ b/components/script/dom/webidls/MediaQueryListEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://drafts.csswg.org/cssom-view/#dom-mediaquerylistevent-mediaquerylistevent
-[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict), Exposed=(Window)]
+[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict = {}), Exposed=(Window)]
 interface MediaQueryListEvent : Event {
   readonly attribute DOMString media;
   readonly attribute boolean matches;
diff --git a/components/script/dom/webidls/MessageEvent.webidl b/components/script/dom/webidls/MessageEvent.webidl
index c2ef9732096..fc43c463743 100644
--- a/components/script/dom/webidls/MessageEvent.webidl
+++ b/components/script/dom/webidls/MessageEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#messageevent
-[Constructor(DOMString type, optional MessageEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional MessageEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface MessageEvent : Event {
   readonly attribute any data;
   readonly attribute DOMString origin;
diff --git a/components/script/dom/webidls/MouseEvent.webidl b/components/script/dom/webidls/MouseEvent.webidl
index 29d5872f65e..ca39c759c04 100644
--- a/components/script/dom/webidls/MouseEvent.webidl
+++ b/components/script/dom/webidls/MouseEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-mouseevent
-[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict),
+[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict = {}),
  Exposed=Window]
 interface MouseEvent : UIEvent {
     readonly    attribute long           screenX;
diff --git a/components/script/dom/webidls/MutationObserver.webidl b/components/script/dom/webidls/MutationObserver.webidl
index 28e59d8244d..a2f223da800 100644
--- a/components/script/dom/webidls/MutationObserver.webidl
+++ b/components/script/dom/webidls/MutationObserver.webidl
@@ -10,7 +10,7 @@
 [Pref="dom.mutation_observer.enabled", Constructor(MutationCallback callback)]
 interface MutationObserver {
     [Throws]
-    void observe(Node target, optional MutationObserverInit options);
+    void observe(Node target, optional MutationObserverInit options = {});
     void disconnect();
     sequence<MutationRecord> takeRecords();
 };
diff --git a/components/script/dom/webidls/Node.webidl b/components/script/dom/webidls/Node.webidl
index 9433e96efa2..37943477bd3 100644
--- a/components/script/dom/webidls/Node.webidl
+++ b/components/script/dom/webidls/Node.webidl
@@ -32,7 +32,7 @@ interface Node : EventTarget {
   readonly attribute Document? ownerDocument;
 
   [Pure]
-  Node getRootNode(optional GetRootNodeOptions options);
+  Node getRootNode(optional GetRootNodeOptions options = {});
 
   [Pure]
   readonly attribute Node? parentNode;
diff --git a/components/script/dom/webidls/OscillatorNode.webidl b/components/script/dom/webidls/OscillatorNode.webidl
index 510b87880a7..ee21e96ffea 100644
--- a/components/script/dom/webidls/OscillatorNode.webidl
+++ b/components/script/dom/webidls/OscillatorNode.webidl
@@ -22,7 +22,7 @@ dictionary OscillatorOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional OscillatorOptions options)]
+ Constructor (BaseAudioContext context, optional OscillatorOptions options = {})]
 interface OscillatorNode : AudioScheduledSourceNode {
   [SetterThrows]
   attribute OscillatorType type;
diff --git a/components/script/dom/webidls/PageTransitionEvent.webidl b/components/script/dom/webidls/PageTransitionEvent.webidl
index 147a2d2e0c1..c2f438a89b5 100644
--- a/components/script/dom/webidls/PageTransitionEvent.webidl
+++ b/components/script/dom/webidls/PageTransitionEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#the-pagetransitionevent-interface
-[Constructor(DOMString type, optional PageTransitionEventInit eventInitDict),
+[Constructor(DOMString type, optional PageTransitionEventInit eventInitDict = {}),
  Exposed=Window]
 interface PageTransitionEvent : Event {
   readonly attribute boolean persisted;
diff --git a/components/script/dom/webidls/PannerNode.webidl b/components/script/dom/webidls/PannerNode.webidl
index 8c9f8f1913e..08733377fef 100644
--- a/components/script/dom/webidls/PannerNode.webidl
+++ b/components/script/dom/webidls/PannerNode.webidl
@@ -35,7 +35,7 @@ enum PanningModelType {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional PannerOptions options)]
+ Constructor (BaseAudioContext context, optional PannerOptions options = {})]
 interface PannerNode : AudioNode {
   attribute PanningModelType panningModel;
   readonly attribute AudioParam positionX;
diff --git a/components/script/dom/webidls/PopStateEvent.webidl b/components/script/dom/webidls/PopStateEvent.webidl
index 933ec3e7efa..1bd7637a647 100644
--- a/components/script/dom/webidls/PopStateEvent.webidl
+++ b/components/script/dom/webidls/PopStateEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#the-popstateevent-interface
-[Constructor(DOMString type, optional PopStateEventInit eventInitDict),
+[Constructor(DOMString type, optional PopStateEventInit eventInitDict = {}),
  Exposed=Window]
 interface PopStateEvent : Event {
   readonly attribute any state;
diff --git a/components/script/dom/webidls/ProgressEvent.webidl b/components/script/dom/webidls/ProgressEvent.webidl
index 4168c2e6b1d..698ec828877 100644
--- a/components/script/dom/webidls/ProgressEvent.webidl
+++ b/components/script/dom/webidls/ProgressEvent.webidl
@@ -12,7 +12,7 @@
  * http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
  */
 
-[Constructor(DOMString type, optional ProgressEventInit eventInitDict),
+[Constructor(DOMString type, optional ProgressEventInit eventInitDict = {}),
  Exposed=(Window,Worker)]
 interface ProgressEvent : Event {
   readonly attribute boolean lengthComputable;
diff --git a/components/script/dom/webidls/PromiseRejectionEvent.webidl b/components/script/dom/webidls/PromiseRejectionEvent.webidl
index 3a1ee3dc128..43eb391ccfc 100644
--- a/components/script/dom/webidls/PromiseRejectionEvent.webidl
+++ b/components/script/dom/webidls/PromiseRejectionEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-promiserejectionevent-interface
 
-[Constructor(DOMString type, optional PromiseRejectionEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional PromiseRejectionEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface PromiseRejectionEvent : Event {
   readonly attribute Promise<any> promise;
   readonly attribute any reason;
diff --git a/components/script/dom/webidls/RTCIceCandidate.webidl b/components/script/dom/webidls/RTCIceCandidate.webidl
index 538805c88db..01fd9a42034 100644
--- a/components/script/dom/webidls/RTCIceCandidate.webidl
+++ b/components/script/dom/webidls/RTCIceCandidate.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
 
 
-[Constructor(optional RTCIceCandidateInit candidateInitDict),
+[Constructor(optional RTCIceCandidateInit candidateInitDict = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCIceCandidate {
     readonly attribute DOMString               candidate;
diff --git a/components/script/dom/webidls/RTCPeerConnection.webidl b/components/script/dom/webidls/RTCPeerConnection.webidl
index 58cb7301ea3..b702a70f71d 100644
--- a/components/script/dom/webidls/RTCPeerConnection.webidl
+++ b/components/script/dom/webidls/RTCPeerConnection.webidl
@@ -4,11 +4,11 @@
 
 // https://w3c.github.io/webrtc-pc/#interface-definition
 
-[Constructor(optional RTCConfiguration configuration),
+[Constructor(optional RTCConfiguration configuration = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCPeerConnection : EventTarget {
-    Promise<RTCSessionDescriptionInit> createOffer(optional RTCOfferOptions options);
-    Promise<RTCSessionDescriptionInit> createAnswer(optional RTCAnswerOptions options);
+    Promise<RTCSessionDescriptionInit> createOffer(optional RTCOfferOptions options = {});
+    Promise<RTCSessionDescriptionInit> createAnswer(optional RTCAnswerOptions options = {});
     Promise<void>                      setLocalDescription(RTCSessionDescriptionInit description);
     readonly attribute RTCSessionDescription? localDescription;
     // readonly attribute RTCSessionDescription? currentLocalDescription;
@@ -17,7 +17,7 @@ interface RTCPeerConnection : EventTarget {
     readonly attribute RTCSessionDescription? remoteDescription;
     // readonly attribute RTCSessionDescription? currentRemoteDescription;
     // readonly attribute RTCSessionDescription? pendingRemoteDescription;
-    Promise<void>                      addIceCandidate(optional RTCIceCandidateInit candidate);
+    Promise<void>                      addIceCandidate(optional RTCIceCandidateInit candidate = {});
     readonly attribute RTCSignalingState      signalingState;
     readonly attribute RTCIceGatheringState   iceGatheringState;
     readonly attribute RTCIceConnectionState  iceConnectionState;
diff --git a/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl b/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
index 26a3919b21f..0d2c2b72879 100644
--- a/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
+++ b/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://w3c.github.io/webrtc-pc/#rtcpeerconnectioniceevent
 
-[Constructor(DOMString type, optional RTCPeerConnectionIceEventInit eventInitDict),
+[Constructor(DOMString type, optional RTCPeerConnectionIceEventInit eventInitDict = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCPeerConnectionIceEvent : Event {
     readonly attribute RTCIceCandidate? candidate;
diff --git a/components/script/dom/webidls/Request.webidl b/components/script/dom/webidls/Request.webidl
index 79c1da9bad5..52f258446f3 100644
--- a/components/script/dom/webidls/Request.webidl
+++ b/components/script/dom/webidls/Request.webidl
@@ -6,7 +6,7 @@
 
 typedef (Request or USVString) RequestInfo;
 
-[Constructor(RequestInfo input, optional RequestInit init),
+[Constructor(RequestInfo input, optional RequestInit init = {}),
  Exposed=(Window,Worker)]
 
 interface Request {
diff --git a/components/script/dom/webidls/Response.webidl b/components/script/dom/webidls/Response.webidl
index eaf8fb8b066..7297d64ae9b 100644
--- a/components/script/dom/webidls/Response.webidl
+++ b/components/script/dom/webidls/Response.webidl
@@ -4,7 +4,7 @@
 
 // https://fetch.spec.whatwg.org/#response-class
 
- [Constructor(optional BodyInit? body = null, optional ResponseInit init),
+ [Constructor(optional BodyInit? body = null, optional ResponseInit init = {}),
   Exposed=(Window,Worker)]
 interface Response {
   [NewObject] static Response error();
diff --git a/components/script/dom/webidls/ServiceWorkerContainer.webidl b/components/script/dom/webidls/ServiceWorkerContainer.webidl
index ec7ae1a43e8..18deb5e58f4 100644
--- a/components/script/dom/webidls/ServiceWorkerContainer.webidl
+++ b/components/script/dom/webidls/ServiceWorkerContainer.webidl
@@ -8,7 +8,8 @@ interface ServiceWorkerContainer : EventTarget {
   readonly attribute ServiceWorker? controller;
   //readonly attribute Promise<ServiceWorkerRegistration> ready;
 
-  [NewObject] Promise<ServiceWorkerRegistration> register(USVString scriptURL, optional RegistrationOptions options);
+  [NewObject] Promise<ServiceWorkerRegistration> register(USVString scriptURL,
+                                                          optional RegistrationOptions options = {});
 
   //[NewObject] Promise<any> getRegistration(optional USVString clientURL = "");
   //[NewObject] Promise<FrozenArray<ServiceWorkerRegistration>> getRegistrations();
diff --git a/components/script/dom/webidls/StereoPannerNode.webidl b/components/script/dom/webidls/StereoPannerNode.webidl
index 69b58a408c1..1795ce79bdf 100644
--- a/components/script/dom/webidls/StereoPannerNode.webidl
+++ b/components/script/dom/webidls/StereoPannerNode.webidl
@@ -11,7 +11,7 @@ dictionary StereoPannerOptions: AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional StereoPannerOptions options)]
+ Constructor (BaseAudioContext context, optional StereoPannerOptions options = {})]
 interface StereoPannerNode : AudioScheduledSourceNode {
   readonly attribute AudioParam pan;
 };
diff --git a/components/script/dom/webidls/StorageEvent.webidl b/components/script/dom/webidls/StorageEvent.webidl
index 72330c77f9e..060a82c0d05 100644
--- a/components/script/dom/webidls/StorageEvent.webidl
+++ b/components/script/dom/webidls/StorageEvent.webidl
@@ -9,7 +9,7 @@
  * Event sent to a window when a storage area changes.
  */
 
-[Constructor(DOMString type, optional StorageEventInit eventInitDict), Exposed=Window]
+[Constructor(DOMString type, optional StorageEventInit eventInitDict = {}), Exposed=Window]
 interface StorageEvent : Event {
   readonly attribute DOMString? key;
   readonly attribute DOMString? oldValue;
diff --git a/components/script/dom/webidls/TestBinding.webidl b/components/script/dom/webidls/TestBinding.webidl
index cc942fd06b8..36f91806d4a 100644
--- a/components/script/dom/webidls/TestBinding.webidl
+++ b/components/script/dom/webidls/TestBinding.webidl
@@ -32,7 +32,7 @@ dictionary TestDictionary {
   Blob interfaceValue;
   any anyValue;
   object objectValue;
-  TestDictionaryDefaults dict = null;
+  TestDictionaryDefaults dict = {};
   sequence<TestDictionaryDefaults> seqDict;
   // Testing codegen to import Element correctly, ensure no other code references Element directly
   sequence<Element> elementSequence;
diff --git a/components/script/dom/webidls/TestWorklet.webidl b/components/script/dom/webidls/TestWorklet.webidl
index 3c5d84d2b09..3be494d4825 100644
--- a/components/script/dom/webidls/TestWorklet.webidl
+++ b/components/script/dom/webidls/TestWorklet.webidl
@@ -7,6 +7,6 @@
 
 [Pref="dom.worklet.testing.enabled", Exposed=(Window), Constructor]
 interface TestWorklet {
-   [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options);
+   [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options = {});
    DOMString? lookup(DOMString key);
 };
diff --git a/components/script/dom/webidls/TextDecoder.webidl b/components/script/dom/webidls/TextDecoder.webidl
index 5f1a0cc881a..a2454ab4e05 100644
--- a/components/script/dom/webidls/TextDecoder.webidl
+++ b/components/script/dom/webidls/TextDecoder.webidl
@@ -12,11 +12,11 @@ dictionary TextDecodeOptions {
   boolean stream = false;
 };
 
-[Constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options), Exposed=(Window,Worker)]
+[Constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options = {}), Exposed=(Window,Worker)]
 interface TextDecoder {
   readonly attribute DOMString encoding;
   readonly attribute boolean fatal;
   readonly attribute boolean ignoreBOM;
   [Throws]
-  USVString decode(optional BufferSource input, optional TextDecodeOptions options);
+  USVString decode(optional BufferSource input, optional TextDecodeOptions options = {});
 };
diff --git a/components/script/dom/webidls/TrackEvent.webidl b/components/script/dom/webidls/TrackEvent.webidl
index 214583e3245..f87fa0472a1 100644
--- a/components/script/dom/webidls/TrackEvent.webidl
+++ b/components/script/dom/webidls/TrackEvent.webidl
@@ -5,7 +5,7 @@
 // https://html.spec.whatwg.org/multipage/#the-trackevent-interface
 
 [Exposed=Window,
- Constructor(DOMString type, optional TrackEventInit eventInitDict)]
+ Constructor(DOMString type, optional TrackEventInit eventInitDict = {})]
 interface TrackEvent : Event {
   readonly attribute (VideoTrack or AudioTrack or TextTrack)? track;
 };
diff --git a/components/script/dom/webidls/TransitionEvent.webidl b/components/script/dom/webidls/TransitionEvent.webidl
index 505d6bc2941..05998ececfb 100644
--- a/components/script/dom/webidls/TransitionEvent.webidl
+++ b/components/script/dom/webidls/TransitionEvent.webidl
@@ -6,7 +6,7 @@
  * https://dom.spec.whatwg.org/#event
  */
 
-[Constructor(DOMString type, optional TransitionEventInit transitionEventInitDict),
+[Constructor(DOMString type, optional TransitionEventInit transitionEventInitDict = {}),
  Exposed=Window]
 interface TransitionEvent : Event {
   readonly attribute DOMString          propertyName;
diff --git a/components/script/dom/webidls/UIEvent.webidl b/components/script/dom/webidls/UIEvent.webidl
index 7e895a34448..20be43aec90 100644
--- a/components/script/dom/webidls/UIEvent.webidl
+++ b/components/script/dom/webidls/UIEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-uievent
-[Constructor(DOMString type, optional UIEventInit eventInitDict)]
+[Constructor(DOMString type, optional UIEventInit eventInitDict = {})]
 interface UIEvent : Event {
   //  readonly    attribute WindowProxy? view;
   readonly attribute Window? view;
diff --git a/components/script/dom/webidls/WebGLContextEvent.webidl b/components/script/dom/webidls/WebGLContextEvent.webidl
index 308f3ec7610..f8a2dbf2137 100644
--- a/components/script/dom/webidls/WebGLContextEvent.webidl
+++ b/components/script/dom/webidls/WebGLContextEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15
-[Constructor(DOMString type, optional WebGLContextEventInit eventInit),
+[Constructor(DOMString type, optional WebGLContextEventInit eventInit = {}),
  Exposed=Window]
 interface WebGLContextEvent : Event {
     readonly attribute DOMString statusMessage;
diff --git a/components/script/dom/webidls/WheelEvent.webidl b/components/script/dom/webidls/WheelEvent.webidl
index a38b87dd97d..b202d7f2c24 100644
--- a/components/script/dom/webidls/WheelEvent.webidl
+++ b/components/script/dom/webidls/WheelEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-wheelevent
-[Constructor(DOMString typeArg, optional WheelEventInit wheelEventInitDict),
+[Constructor(DOMString typeArg, optional WheelEventInit wheelEventInitDict = {}),
  Exposed=Window]
 interface WheelEvent : MouseEvent {
     const unsigned long DOM_DELTA_PIXEL = 0x00;
diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index 81ffee9283e..56d9d06a819 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -118,11 +118,11 @@ partial interface Window {
   [Replaceable] readonly attribute long pageXOffset;
   [Replaceable] readonly attribute long scrollY;
   [Replaceable] readonly attribute long pageYOffset;
-  void scroll(optional ScrollToOptions options);
+  void scroll(optional ScrollToOptions options = {});
   void scroll(unrestricted double x, unrestricted double y);
-  void scrollTo(optional ScrollToOptions options);
+  void scrollTo(optional ScrollToOptions options = {});
   void scrollTo(unrestricted double x, unrestricted double y);
-  void scrollBy(optional ScrollToOptions options);
+  void scrollBy(optional ScrollToOptions options = {});
   void scrollBy(unrestricted double x, unrestricted double y);
 
   // client
diff --git a/components/script/dom/webidls/Worker.webidl b/components/script/dom/webidls/Worker.webidl
index 2c17e459fa8..f09b565f31a 100644
--- a/components/script/dom/webidls/Worker.webidl
+++ b/components/script/dom/webidls/Worker.webidl
@@ -9,7 +9,7 @@ interface AbstractWorker {
 };
 
 // https://html.spec.whatwg.org/multipage/#worker
-[Constructor(USVString scriptURL, optional WorkerOptions options), Exposed=(Window,Worker)]
+[Constructor(USVString scriptURL, optional WorkerOptions options = {}), Exposed=(Window,Worker)]
 interface Worker : EventTarget {
   void terminate();
 
diff --git a/components/script/dom/webidls/Worklet.webidl b/components/script/dom/webidls/Worklet.webidl
index 9e954925ab0..16ec8e8d7c9 100644
--- a/components/script/dom/webidls/Worklet.webidl
+++ b/components/script/dom/webidls/Worklet.webidl
@@ -5,7 +5,7 @@
 // https://drafts.css-houdini.org/worklets/#worklet
 [Pref="dom.worklet.enabled", Exposed=(Window)]
 interface Worklet {
-    [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options);
+    [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options = {});
 };
 
 dictionary WorkletOptions {
diff --git a/components/script/dom/webidls/XR.webidl b/components/script/dom/webidls/XR.webidl
index 58732edd42b..0b3debeaee6 100644
--- a/components/script/dom/webidls/XR.webidl
+++ b/components/script/dom/webidls/XR.webidl
@@ -7,7 +7,7 @@
 interface XR: EventTarget {
   // Methods
   Promise<void> supportsSessionMode(XRSessionMode mode);
-  Promise<XRSession> requestSession(optional XRSessionCreationOptions parameters);
+  Promise<XRSession> requestSession(optional XRSessionCreationOptions parameters = {});
 
   // Events
   // attribute EventHandler ondevicechange;
diff --git a/components/script/dom/webidls/XRRigidTransform.webidl b/components/script/dom/webidls/XRRigidTransform.webidl
index 089dc1732a6..b58a8c339e4 100644
--- a/components/script/dom/webidls/XRRigidTransform.webidl
+++ b/components/script/dom/webidls/XRRigidTransform.webidl
@@ -5,7 +5,7 @@
 // https://immersive-web.github.io/webxr/#xrrigidtransform-interface
 
 [SecureContext, Exposed=Window, Pref="dom.webxr.enabled",
- Constructor(optional DOMPointInit position, optional DOMPointInit orientation)]
+ Constructor(optional DOMPointInit position = {}, optional DOMPointInit orientation = {})]
 interface XRRigidTransform {
   readonly attribute DOMPointReadOnly position;
   readonly attribute DOMPointReadOnly orientation;
diff --git a/components/script/dom/webidls/XRSession.webidl b/components/script/dom/webidls/XRSession.webidl
index 59ccecb521a..d35f724f87e 100644
--- a/components/script/dom/webidls/XRSession.webidl
+++ b/components/script/dom/webidls/XRSession.webidl
@@ -29,7 +29,7 @@ interface XRSession : EventTarget {
   // FrozenArray<XRInputSource> getInputSources();
   sequence<XRInputSource> getInputSources();
 
-  void updateRenderState(optional XRRenderStateInit state);
+  void updateRenderState(optional XRRenderStateInit state = {});
   long requestAnimationFrame(XRFrameRequestCallback callback);
   void cancelAnimationFrame(long handle);
 
diff --git a/components/script/dom/webidls/XRWebGLLayer.webidl b/components/script/dom/webidls/XRWebGLLayer.webidl
index 0df8296be34..f551096fc05 100644
--- a/components/script/dom/webidls/XRWebGLLayer.webidl
+++ b/components/script/dom/webidls/XRWebGLLayer.webidl
@@ -19,7 +19,7 @@ dictionary XRWebGLLayerInit {
 
 [SecureContext, Exposed=Window, Constructor(XRSession session,
             XRWebGLRenderingContext context,
-            optional XRWebGLLayerInit layerInit),
+            optional XRWebGLLayerInit layerInit = {}),
     Pref="dom.webxr.enabled"]
 interface XRWebGLLayer : XRLayer {
   // // Attributes
diff --git a/components/script_plugins/Cargo.toml b/components/script_plugins/Cargo.toml
index 407d4639939..f1537b655a0 100644
--- a/components/script_plugins/Cargo.toml
+++ b/components/script_plugins/Cargo.toml
@@ -14,4 +14,4 @@ unrooted_must_root_lint = []
 webidl_lint = []
 
 [dependencies]
-weedle = "0.9"
+weedle = "0.10"