Convert Web IDL void to undefined

Fixes #27660

36 files changed, 286 insertions, 286 deletions

diff --git a/components/script/dom/bindings/codegen/parser/WebIDL.py b/components/script/dom/bindings/codegen/parser/WebIDL.py
index d74278c3e0c..85c0046549d 100644
--- a/components/script/dom/bindings/codegen/parser/WebIDL.py
+++ b/components/script/dom/bindings/codegen/parser/WebIDL.py
@@ -2093,7 +2093,7 @@ class IDLType(IDLObject):
         'utf8string',
         'jsstring',
         'object',
-        'void',
+        'undefined',
         # Funny stuff
         'interface',
         'dictionary',
@@ -2168,8 +2168,8 @@ class IDLType(IDLObject):
     def isJSString(self):
         return False
 
-    def isVoid(self):
-        return self.name == "Void"
+    def isUndefined(self):
+        return self.name == "Undefined"
 
     def isSequence(self):
         return False
@@ -2355,7 +2355,7 @@ class IDLParametrizedType(IDLType):
 
 class IDLNullableType(IDLParametrizedType):
     def __init__(self, location, innerType):
-        assert not innerType.isVoid()
+        assert not innerType.isUndefined()
         assert not innerType == BuiltinTypes[IDLBuiltinType.Types.any]
 
         IDLParametrizedType.__init__(self, location, None, innerType)
@@ -2414,7 +2414,7 @@ class IDLNullableType(IDLParametrizedType):
     def isInteger(self):
         return self.inner.isInteger()
 
-    def isVoid(self):
+    def isUndefined(self):
         return False
 
     def isSequence(self):
@@ -2517,7 +2517,7 @@ class IDLNullableType(IDLParametrizedType):
 
 class IDLSequenceType(IDLParametrizedType):
     def __init__(self, location, parameterType):
-        assert not parameterType.isVoid()
+        assert not parameterType.isUndefined()
 
         IDLParametrizedType.__init__(self, location, parameterType.name, parameterType)
         # Need to set self.name up front if our inner type is already complete,
@@ -2561,7 +2561,7 @@ class IDLSequenceType(IDLParametrizedType):
     def isJSString(self):
         return False
 
-    def isVoid(self):
+    def isUndefined(self):
         return False
 
     def isSequence(self):
@@ -2602,7 +2602,7 @@ class IDLRecordType(IDLParametrizedType):
     def __init__(self, location, keyType, valueType):
         assert keyType.isString()
         assert keyType.isComplete()
-        assert not valueType.isVoid()
+        assert not valueType.isUndefined()
 
         IDLParametrizedType.__init__(self, location, valueType.name, valueType)
         self.keyType = keyType
@@ -2673,7 +2673,7 @@ class IDLUnionType(IDLType):
     def prettyName(self):
         return "(" + " or ".join(m.prettyName() for m in self.memberTypes) + ")"
 
-    def isVoid(self):
+    def isUndefined(self):
         return False
 
     def isUnion(self):
@@ -2836,8 +2836,8 @@ class IDLTypedefType(IDLType):
     def isJSString(self):
         return self.inner.isJSString()
 
-    def isVoid(self):
-        return self.inner.isVoid()
+    def isUndefined(self):
+        return self.inner.isUndefined()
 
     def isJSONType(self):
         return self.inner.isJSONType()
@@ -2972,7 +2972,7 @@ class IDLWrapperType(IDLType):
     def isJSString(self):
         return False
 
-    def isVoid(self):
+    def isUndefined(self):
         return False
 
     def isSequence(self):
@@ -3178,7 +3178,7 @@ class IDLBuiltinType(IDLType):
         'utf8string',
         'jsstring',
         'object',
-        'void',
+        'undefined',
         # Funny stuff
         'ArrayBuffer',
         'ArrayBufferView',
@@ -3215,7 +3215,7 @@ class IDLBuiltinType(IDLType):
         Types.utf8string: IDLType.Tags.utf8string,
         Types.jsstring: IDLType.Tags.jsstring,
         Types.object: IDLType.Tags.object,
-        Types.void: IDLType.Tags.void,
+        Types.undefined: IDLType.Tags.undefined,
         Types.ArrayBuffer: IDLType.Tags.interface,
         Types.ArrayBufferView: IDLType.Tags.interface,
         Types.Int8Array: IDLType.Tags.interface,
@@ -3251,7 +3251,7 @@ class IDLBuiltinType(IDLType):
         Types.utf8string: "USVString", # That's what it is in spec terms
         Types.jsstring: "USVString", # Again, that's what it is in spec terms
         Types.object: "object",
-        Types.void: "void",
+        Types.undefined: "undefined",
         Types.ArrayBuffer: "ArrayBuffer",
         Types.ArrayBufferView: "ArrayBufferView",
         Types.Int8Array: "Int8Array",
@@ -3456,8 +3456,8 @@ class IDLBuiltinType(IDLType):
             return False
         if self.isObject():
             return other.isPrimitive() or other.isString() or other.isEnum()
-        if self.isVoid():
-            return not other.isVoid()
+        if self.isUndefined():
+            return not other.isUndefined()
         # Not much else we could be!
         assert self.isSpiderMonkeyInterface()
         # Like interfaces, but we know we're not a callback
@@ -3591,9 +3591,9 @@ BuiltinTypes = {
     IDLBuiltinType.Types.object:
         IDLBuiltinType(BuiltinLocation("<builtin type>"), "Object",
                        IDLBuiltinType.Types.object),
-    IDLBuiltinType.Types.void:
-        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Void",
-                       IDLBuiltinType.Types.void),
+    IDLBuiltinType.Types.undefined:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Undefined",
+                       IDLBuiltinType.Types.undefined),
     IDLBuiltinType.Types.ArrayBuffer:
         IDLBuiltinType(BuiltinLocation("<builtin type>"), "ArrayBuffer",
                        IDLBuiltinType.Types.ArrayBuffer),
@@ -4196,9 +4196,9 @@ class IDLIterable(IDLMaplikeOrSetlikeOrIterableBase):
         self.addMethod("values", members, False, self.iteratorType,
                        affectsNothing=True, newObject=True)
 
-        # void forEach(callback(valueType, keyType), optional any thisArg)
+        # undefined forEach(callback(valueType, keyType), optional any thisArg)
         self.addMethod("forEach", members, False,
-                       BuiltinTypes[IDLBuiltinType.Types.void],
+                       BuiltinTypes[IDLBuiltinType.Types.undefined],
                        self.getForEachArguments())
 
     def isValueIterator(self):
@@ -4256,8 +4256,8 @@ class IDLMaplikeOrSetlike(IDLMaplikeOrSetlikeOrIterableBase):
         self.addMethod("values", members, False, BuiltinTypes[IDLBuiltinType.Types.object],
                        affectsNothing=True, isIteratorAlias=self.isSetlike())
 
-        # void forEach(callback(valueType, keyType), thisVal)
-        self.addMethod("forEach", members, False, BuiltinTypes[IDLBuiltinType.Types.void],
+        # undefined forEach(callback(valueType, keyType), thisVal)
+        self.addMethod("forEach", members, False, BuiltinTypes[IDLBuiltinType.Types.undefined],
                        self.getForEachArguments())
 
         def getKeyArg():
@@ -4270,8 +4270,8 @@ class IDLMaplikeOrSetlike(IDLMaplikeOrSetlikeOrIterableBase):
                        [getKeyArg()], isPure=True)
 
         if not self.readonly:
-            # void clear()
-            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.void],
+            # undefined clear()
+            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.undefined],
                            [])
             # boolean delete(keyType key)
             self.addMethod("delete", members, True,
@@ -4280,8 +4280,8 @@ class IDLMaplikeOrSetlike(IDLMaplikeOrSetlikeOrIterableBase):
         # Always generate underscored functions (e.g. __add, __clear) for js
         # implemented interfaces as convenience functions.
         if isJSImplemented:
-            # void clear()
-            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.void],
+            # undefined clear()
+            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.undefined],
                            [], chromeOnly=True)
             # boolean delete(keyType key)
             self.addMethod("delete", members, True,
@@ -5119,7 +5119,7 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
             assert (arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.domstring] or
                     arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.unsigned_long])
             assert not arguments[0].optional and not arguments[0].variadic
-            assert not self._getter or not overload.returnType.isVoid()
+            assert not self._getter or not overload.returnType.isUndefined()
 
         if self._setter:
             assert len(self._overloads) == 1
@@ -5480,8 +5480,8 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
             # This is called before we've done overload resolution
             overloads = self._overloads
             assert len(overloads) == 1
-            if not overloads[0].returnType.isVoid():
-                raise WebIDLError("[LenientFloat] used on a non-void method",
+            if not overloads[0].returnType.isUndefined():
+                raise WebIDLError("[LenientFloat] used on a non-undefined returning method",
                                   [attr.location, self.location])
             if not overloads[0].includesRestrictedFloatArgument():
                 raise WebIDLError("[LenientFloat] used on an operation with no "
@@ -5837,7 +5837,7 @@ class Tokenizer(object):
         "record": "RECORD",
         "short": "SHORT",
         "unsigned": "UNSIGNED",
-        "void": "VOID",
+        "undefined": "UNDEFINED",
         ":": "COLON",
         ";": "SEMICOLON",
         "{": "LBRACE",
@@ -6722,8 +6722,8 @@ class Parser(Tokenizer):
                                    "optional" if arguments[0].optional else "variadic"),
                                   [arguments[0].location])
         if getter:
-            if returnType.isVoid():
-                raise WebIDLError("getter cannot have void return type",
+            if returnType.isUndefined():
+                raise WebIDLError("getter cannot have undefined return type",
                                   [self.getLocation(p, 2)])
         if setter:
             if len(arguments) != 2:
@@ -7103,7 +7103,7 @@ class Parser(Tokenizer):
                   | SYMBOL
                   | TRUE
                   | UNSIGNED
-                  | VOID
+                  | UNDEFINED
                   | ArgumentNameKeyword
         """
         pass
@@ -7145,7 +7145,7 @@ class Parser(Tokenizer):
         """
         p[0] = BuiltinTypes[IDLBuiltinType.Types.any]
 
-    # Note: Promise<void> is allowed, so we want to parametrize on ReturnType,
+    # Note: Promise<undefined> 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):
         """
@@ -7413,11 +7413,11 @@ class Parser(Tokenizer):
         """
         p[0] = p[1]
 
-    def p_ReturnTypeVoid(self, p):
+    def p_ReturnTypeUndefined(self, p):
         """
-            ReturnType : VOID
+            ReturnType : UNDEFINED
         """
-        p[0] = BuiltinTypes[IDLBuiltinType.Types.void]
+        p[0] = BuiltinTypes[IDLBuiltinType.Types.undefined]
 
     def p_ScopedName(self, p):
         """
@@ -7564,7 +7564,7 @@ class Parser(Tokenizer):
 
     def parse(self, t, filename=None):
         self._filename = filename
-        self.lexer.input(t.decode(encoding = 'utf-8'))
+        self.lexer.input(t)
 
         # for tok in iter(self.lexer.token, None):
         #    print tok
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_argument_identifier_conflicts.py b/components/script/dom/bindings/codegen/parser/tests/test_argument_identifier_conflicts.py
index eb1f6d3c92e..9ae85531fa3 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_argument_identifier_conflicts.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_argument_identifier_conflicts.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface ArgumentIdentifierConflict {
-              void foo(boolean arg1, boolean arg1);
+              undefined foo(boolean arg1, boolean arg1);
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_argument_keywords.py b/components/script/dom/bindings/codegen/parser/tests/test_argument_keywords.py
index e190f617e26..2b29658d678 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_argument_keywords.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_argument_keywords.py
@@ -1,7 +1,7 @@
 def WebIDLTest(parser, harness):
     parser.parse("""
     interface Foo {
-      void foo(object constructor);
+      undefined foo(object constructor);
     };
     """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_argument_novoid.py b/components/script/dom/bindings/codegen/parser/tests/test_argument_novoid.py
index ef8c2229aed..42e0776e677 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_argument_novoid.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_argument_novoid.py
@@ -2,8 +2,8 @@ def WebIDLTest(parser, harness):
     threw = False
     try:
         parser.parse("""
-            interface VoidArgument1 {
-              void foo(void arg2);
+            interface UndefinedArgument1 {
+              undefined foo(undefined arg2);
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_arraybuffer.py b/components/script/dom/bindings/codegen/parser/tests/test_arraybuffer.py
index 4a96c0ff512..7020db59f3e 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_arraybuffer.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_arraybuffer.py
@@ -4,37 +4,37 @@ def WebIDLTest(parser, harness):
     parser.parse("""
         interface TestArrayBuffer {
           attribute ArrayBuffer bufferAttr;
-          void bufferMethod(ArrayBuffer arg1, ArrayBuffer? arg2, sequence<ArrayBuffer> arg3);
+          undefined bufferMethod(ArrayBuffer arg1, ArrayBuffer? arg2, sequence<ArrayBuffer> arg3);
 
           attribute ArrayBufferView viewAttr;
-          void viewMethod(ArrayBufferView arg1, ArrayBufferView? arg2, sequence<ArrayBufferView> arg3);
+          undefined viewMethod(ArrayBufferView arg1, ArrayBufferView? arg2, sequence<ArrayBufferView> arg3);
 
           attribute Int8Array int8ArrayAttr;
-          void int8ArrayMethod(Int8Array arg1, Int8Array? arg2, sequence<Int8Array> arg3);
+          undefined int8ArrayMethod(Int8Array arg1, Int8Array? arg2, sequence<Int8Array> arg3);
 
           attribute Uint8Array uint8ArrayAttr;
-          void uint8ArrayMethod(Uint8Array arg1, Uint8Array? arg2, sequence<Uint8Array> arg3);
+          undefined uint8ArrayMethod(Uint8Array arg1, Uint8Array? arg2, sequence<Uint8Array> arg3);
 
           attribute Uint8ClampedArray uint8ClampedArrayAttr;
-          void uint8ClampedArrayMethod(Uint8ClampedArray arg1, Uint8ClampedArray? arg2, sequence<Uint8ClampedArray> arg3);
+          undefined uint8ClampedArrayMethod(Uint8ClampedArray arg1, Uint8ClampedArray? arg2, sequence<Uint8ClampedArray> arg3);
 
           attribute Int16Array int16ArrayAttr;
-          void int16ArrayMethod(Int16Array arg1, Int16Array? arg2, sequence<Int16Array> arg3);
+          undefined int16ArrayMethod(Int16Array arg1, Int16Array? arg2, sequence<Int16Array> arg3);
 
           attribute Uint16Array uint16ArrayAttr;
-          void uint16ArrayMethod(Uint16Array arg1, Uint16Array? arg2, sequence<Uint16Array> arg3);
+          undefined uint16ArrayMethod(Uint16Array arg1, Uint16Array? arg2, sequence<Uint16Array> arg3);
 
           attribute Int32Array int32ArrayAttr;
-          void int32ArrayMethod(Int32Array arg1, Int32Array? arg2, sequence<Int32Array> arg3);
+          undefined int32ArrayMethod(Int32Array arg1, Int32Array? arg2, sequence<Int32Array> arg3);
 
           attribute Uint32Array uint32ArrayAttr;
-          void uint32ArrayMethod(Uint32Array arg1, Uint32Array? arg2, sequence<Uint32Array> arg3);
+          undefined uint32ArrayMethod(Uint32Array arg1, Uint32Array? arg2, sequence<Uint32Array> arg3);
 
           attribute Float32Array float32ArrayAttr;
-          void float32ArrayMethod(Float32Array arg1, Float32Array? arg2, sequence<Float32Array> arg3);
+          undefined float32ArrayMethod(Float32Array arg1, Float32Array? arg2, sequence<Float32Array> arg3);
 
           attribute Float64Array float64ArrayAttr;
-          void float64ArrayMethod(Float64Array arg1, Float64Array? arg2, sequence<Float64Array> arg3);
+          undefined float64ArrayMethod(Float64Array arg1, Float64Array? arg2, sequence<Float64Array> arg3);
         };
     """)
 
@@ -55,7 +55,7 @@ def WebIDLTest(parser, harness):
         harness.ok(attr.type.isSpiderMonkeyInterface(), "Should test as a js interface")
 
         (retType, arguments) = method.signatures()[0]
-        harness.ok(retType.isVoid(), "Should have a void return type")
+        harness.ok(retType.isUndefined(), "Should have a undefined return type")
         harness.check(len(arguments), 3, "Expect 3 arguments")
 
         harness.check(str(arguments[0].type), t,  "Expect an ArrayBuffer type")
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_attributes_on_types.py b/components/script/dom/bindings/codegen/parser/tests/test_attributes_on_types.py
index ff08791d16f..9ba39018c77 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_attributes_on_types.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_attributes_on_types.py
@@ -20,16 +20,16 @@ def WebIDLTest(parser, harness):
                 attribute [EnforceRange] long foo;
                 attribute [Clamp] long bar;
                 attribute [TreatNullAs=EmptyString] DOMString baz;
-                void method([EnforceRange] long foo, [Clamp] long bar,
+                undefined method([EnforceRange] long foo, [Clamp] long bar,
                             [TreatNullAs=EmptyString] DOMString baz);
-                void method2(optional [EnforceRange] long foo, optional [Clamp] long bar,
+                undefined method2(optional [EnforceRange] long foo, optional [Clamp] long bar,
                              optional [TreatNullAs=EmptyString] DOMString baz);
             };
             interface C {
                 attribute [EnforceRange] long? foo;
                 attribute [Clamp] long? bar;
-                void method([EnforceRange] long? foo, [Clamp] long? bar);
-                void method2(optional [EnforceRange] long? foo, optional [Clamp] long? bar);
+                undefined method([EnforceRange] long? foo, [Clamp] long? bar);
+                undefined method2(optional [EnforceRange] long? foo, optional [Clamp] long? bar);
             };
             interface Setlike {
                 setlike<[Clamp] long>;
@@ -98,13 +98,13 @@ def WebIDLTest(parser, harness):
             interface B {
                 attribute Foo typedefFoo;
                 attribute [AllowShared] ArrayBufferView foo;
-                void method([AllowShared] ArrayBufferView foo);
-                void method2(optional [AllowShared] ArrayBufferView foo);
+                undefined method([AllowShared] ArrayBufferView foo);
+                undefined method2(optional [AllowShared] ArrayBufferView foo);
             };
             interface C {
                 attribute [AllowShared] ArrayBufferView? foo;
-                void method([AllowShared] ArrayBufferView? foo);
-                void method2(optional [AllowShared] ArrayBufferView? foo);
+                undefined method([AllowShared] ArrayBufferView? foo);
+                undefined method2(optional [AllowShared] ArrayBufferView? foo);
             };
             interface Setlike {
                 setlike<[AllowShared] ArrayBufferView>;
@@ -154,7 +154,7 @@ def WebIDLTest(parser, harness):
         """),
         ("optional arguments", """
             interface Foo {
-                void foo(%s optional %s foo);
+                undefined foo(%s optional %s foo);
             };
         """),
         ("typedefs", """
@@ -189,7 +189,7 @@ def WebIDLTest(parser, harness):
         """),
         ("partial interface","""
             interface Foo {
-              void foo();
+              undefined foo();
             };
             %s
             partial interface Foo {
@@ -210,7 +210,7 @@ def WebIDLTest(parser, harness):
         """),
         ("partial namespace","""
             namespace Foo {
-              void foo();
+              undefined foo();
             };
             %s
             partial namespace Foo {
@@ -387,7 +387,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Foo {
-               void foo([Clamp] Bar arg);
+               undefined foo([Clamp] Bar arg);
             };
             typedef long Bar;
         """)
@@ -403,7 +403,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Foo {
-               void foo(Bar arg);
+               undefined foo(Bar arg);
             };
             typedef [Clamp] long Bar;
         """)
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_bytestring.py b/components/script/dom/bindings/codegen/parser/tests/test_bytestring.py
index fa83e9e2d57..51289f5db6e 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_bytestring.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_bytestring.py
@@ -60,8 +60,8 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface OptionalByteString {
-              void passByteString(optional ByteString arg = "hello");
-              };
+              undefined passByteString(optional ByteString arg = "hello");
+            };
         """)
         results2 = parser.finish();
     except WebIDL.WebIDLError as e:
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_callback_interface.py b/components/script/dom/bindings/codegen/parser/tests/test_callback_interface.py
index e4789dae168..34813bcab99 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_callback_interface.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_callback_interface.py
@@ -48,31 +48,31 @@ def WebIDLTest(parser, harness):
     parser = parser.reset()
     parser.parse("""
         callback interface TestCallbackInterface1 {
-          void foo();
+          undefined foo();
         };
         callback interface TestCallbackInterface2 {
-          void foo(DOMString arg);
-          void foo(TestCallbackInterface1 arg);
+          undefined foo(DOMString arg);
+          undefined foo(TestCallbackInterface1 arg);
         };
         callback interface TestCallbackInterface3 {
-          void foo(DOMString arg);
-          void foo(TestCallbackInterface1 arg);
-          static void bar();
+          undefined foo(DOMString arg);
+          undefined foo(TestCallbackInterface1 arg);
+          static undefined bar();
         };
         callback interface TestCallbackInterface4 {
-          void foo(DOMString arg);
-          void foo(TestCallbackInterface1 arg);
-          static void bar();
+          undefined foo(DOMString arg);
+          undefined foo(TestCallbackInterface1 arg);
+          static undefined bar();
           const long baz = 5;
         };
         callback interface TestCallbackInterface5 {
           static attribute boolean bool;
-          void foo();
+          undefined foo();
         };
         callback interface TestCallbackInterface6 {
-          void foo(DOMString arg);
-          void foo(TestCallbackInterface1 arg);
-          void bar();
+          undefined foo(DOMString arg);
+          undefined foo(TestCallbackInterface1 arg);
+          undefined bar();
         };
         callback interface TestCallbackInterface7 {
           static attribute boolean bool;
@@ -81,10 +81,10 @@ def WebIDLTest(parser, harness):
           attribute boolean bool;
         };
         callback interface TestCallbackInterface9 : TestCallbackInterface1 {
-          void foo();
+          undefined foo();
         };
         callback interface TestCallbackInterface10 : TestCallbackInterface1 {
-          void bar();
+          undefined bar();
         };
     """)
     results = parser.finish()
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 f726907c2fc..ebc688bfd9c 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_cereactions.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Foo {
-              [CEReactions(DOMString a)] void foo(boolean arg2);
+              [CEReactions(DOMString a)] undefined foo(boolean arg2);
             };
         """)
 
@@ -47,7 +47,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Foo {
-              [CEReactions] void foo(boolean arg2);
+              [CEReactions] undefined foo(boolean arg2);
             };
         """)
 
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 3cad3022389..dcdc43d5c47 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_dictionary.py
@@ -158,7 +158,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(A arg);
+              undefined doFoo(A arg);
             };
         """)
         results = parser.finish()
@@ -174,7 +174,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional A arg);
+              undefined doFoo(optional A arg);
             };
         """)
         results = parser.finish()
@@ -190,7 +190,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo((A or DOMString) arg);
+              undefined doFoo((A or DOMString) arg);
             };
         """)
         results = parser.finish()
@@ -207,7 +207,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional (A or DOMString) arg);
+              undefined doFoo(optional (A or DOMString) arg);
             };
         """)
         results = parser.finish()
@@ -224,7 +224,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(A arg1, optional long arg2);
+              undefined doFoo(A arg1, optional long arg2);
             };
         """)
         results = parser.finish()
@@ -240,7 +240,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional A arg1, optional long arg2);
+              undefined doFoo(optional A arg1, optional long arg2);
             };
         """)
         results = parser.finish()
@@ -256,7 +256,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(A arg1, optional long arg2, long arg3);
+              undefined doFoo(A arg1, optional long arg2, long arg3);
             };
         """)
         results = parser.finish()
@@ -273,7 +273,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo((A or DOMString) arg1, optional long arg2);
+              undefined doFoo((A or DOMString) arg1, optional long arg2);
             };
         """)
         results = parser.finish()
@@ -291,7 +291,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional (A or DOMString) arg1, optional long arg2);
+              undefined doFoo(optional (A or DOMString) arg1, optional long arg2);
             };
         """)
         results = parser.finish()
@@ -307,7 +307,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(A arg1, long arg2);
+              undefined doFoo(A arg1, long arg2);
             };
         """)
     results = parser.finish()
@@ -320,7 +320,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional A? arg1 = {});
+              undefined doFoo(optional A? arg1 = {});
             };
         """)
         results = parser.finish()
@@ -339,7 +339,7 @@ def WebIDLTest(parser, harness):
               required long x;
             };
             interface X {
-              void doFoo(A? arg1);
+              undefined doFoo(A? arg1);
             };
         """)
         results = parser.finish()
@@ -358,7 +358,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional (A or long)? arg1 = {});
+              undefined doFoo(optional (A or long)? arg1 = {});
             };
         """)
         results = parser.finish()
@@ -378,7 +378,7 @@ def WebIDLTest(parser, harness):
               required long x;
             };
             interface X {
-              void doFoo((A or long)? arg1);
+              undefined doFoo((A or long)? arg1);
             };
         """)
         results = parser.finish()
@@ -397,7 +397,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(sequence<A?> arg1);
+              undefined doFoo(sequence<A?> arg1);
             };
         """)
         results = parser.finish()
@@ -414,7 +414,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional (A or long?) arg1);
+              undefined doFoo(optional (A or long?) arg1);
             };
         """)
         results = parser.finish()
@@ -430,7 +430,7 @@ def WebIDLTest(parser, harness):
             dictionary A {
             };
             interface X {
-              void doFoo(optional (long? or A) arg1);
+              undefined doFoo(optional (long? or A) arg1);
             };
         """)
         results = parser.finish()
@@ -455,7 +455,7 @@ def WebIDLTest(parser, harness):
         dictionary A {
         };
         interface X {
-          void doFoo(optional A arg = {});
+          undefined doFoo(optional A arg = {});
         };
     """)
     results = parser.finish()
@@ -466,7 +466,7 @@ def WebIDLTest(parser, harness):
         dictionary A {
         };
         interface X {
-          void doFoo(optional (A or DOMString) arg = {});
+          undefined doFoo(optional (A or DOMString) arg = {});
         };
     """)
     results = parser.finish()
@@ -477,7 +477,7 @@ def WebIDLTest(parser, harness):
         dictionary A {
         };
         interface X {
-          void doFoo(optional (A or DOMString) arg = "abc");
+          undefined doFoo(optional (A or DOMString) arg = "abc");
         };
     """)
     results = parser.finish()
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 505b36468d6..1fa12832d7f 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_distinguishability.py
@@ -12,10 +12,10 @@ def WebIDLTest(parser, harness):
       };
       interface Bar {
         // Bit of a pain to get things that have dictionary types
-        void passDict(Dict arg);
-        void passFoo(Foo arg);
-        void passNullableUnion((object? or DOMString) arg);
-        void passNullable(Foo? arg);
+        undefined passDict(Dict arg);
+        undefined passFoo(Foo arg);
+        undefined passNullableUnion((object? or DOMString) arg);
+        undefined passNullable(Foo? arg);
       };
     """)
     results = parser.finish()
@@ -56,13 +56,13 @@ def WebIDLTest(parser, harness):
     parser = parser.reset()
     parser.parse("""
       interface TestIface {
-        void passKid(Kid arg);
-        void passParent(Parent arg);
-        void passGrandparent(Grandparent arg);
-        void passUnrelated1(Unrelated1 arg);
-        void passUnrelated2(Unrelated2 arg);
-        void passArrayBuffer(ArrayBuffer arg);
-        void passArrayBuffer(ArrayBufferView arg);
+        undefined passKid(Kid arg);
+        undefined passParent(Parent arg);
+        undefined passGrandparent(Grandparent arg);
+        undefined passUnrelated1(Unrelated1 arg);
+        undefined passUnrelated2(Unrelated2 arg);
+        undefined passArrayBuffer(ArrayBuffer arg);
+        undefined passArrayBuffer(ArrayBufferView arg);
       };
 
       interface Kid : Parent {};
@@ -97,10 +97,10 @@ def WebIDLTest(parser, harness):
     parser.parse("""
       interface Dummy {};
       interface TestIface {
-        void method(long arg1, TestIface arg2);
-        void method(long arg1, long arg2);
-        void method(long arg1, Dummy arg2);
-        void method(DOMString arg1, DOMString arg2, DOMString arg3);
+        undefined method(long arg1, TestIface arg2);
+        undefined method(long arg1, long arg2);
+        undefined method(long arg1, Dummy arg2);
+        undefined method(DOMString arg1, DOMString arg2, DOMString arg3);
       };
     """)
     results = parser.finish()
@@ -115,10 +115,10 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface Dummy {};
           interface TestIface {
-            void method(long arg1, TestIface arg2);
-            void method(long arg1, long arg2);
-            void method(any arg1,  Dummy arg2);
-            void method(DOMString arg1, DOMString arg2, DOMString arg3);
+            undefined method(long arg1, TestIface arg2);
+            undefined method(long arg1, long arg2);
+            undefined method(any arg1,  Dummy arg2);
+            undefined method(DOMString arg1, DOMString arg2, DOMString arg3);
           };
         """)
         results = parser.finish()
@@ -135,10 +135,10 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface Dummy {};
           interface TestIface {
-            void method(long arg1, TestIface arg2);
-            void method(long arg1, long arg2);
-            void method(any arg1,  DOMString arg2);
-            void method(DOMString arg1, DOMString arg2, DOMString arg3);
+            undefined method(long arg1, TestIface arg2);
+            undefined method(long arg1, long arg2);
+            undefined method(any arg1,  DOMString arg2);
+            undefined method(DOMString arg1, DOMString arg2, DOMString arg3);
           };
         """)
         results = parser.finish()
@@ -272,7 +272,7 @@ def WebIDLTest(parser, harness):
           };
         """
         methodTemplate = """
-            void myMethod(%s arg);"""
+            undefined myMethod(%s arg);"""
         methods = (methodTemplate % type1) + (methodTemplate % type2)
         idl = idlTemplate % methods
         parser = parser.reset()
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 a713266c88e..5f04c6ae751 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
@@ -19,7 +19,7 @@ def WebIDLTest(parser, harness):
 
     parser.parse("""
         interface X {
-          void foo(optional sequence<long> arg = []);
+          undefined foo(optional sequence<long> arg = []);
         };
     """)
     results = parser.finish();
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_enum.py b/components/script/dom/bindings/codegen/parser/tests/test_enum.py
index 86228939181..c5617ead99a 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_enum.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_enum.py
@@ -71,7 +71,7 @@ def WebIDLTest(parser, harness):
             "c"
           };
           interface TestInterface {
-            void foo(optional Enum e = "d");
+            undefined foo(optional Enum e = "d");
           };
         """)
         results = parser.finish()
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 e0241a56426..39993eaeae5 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
@@ -8,7 +8,7 @@ def WebIDLTest(parser, harness):
 
       [Exposed=(Foo,Bar1)]
       interface Iface {
-        void method1();
+        undefined method1();
 
         [Exposed=Bar1]
         readonly attribute any attr;
@@ -16,7 +16,7 @@ def WebIDLTest(parser, harness):
 
       [Exposed=Foo]
       partial interface Iface {
-        void method2();
+        undefined method2();
       };
     """)
 
@@ -57,7 +57,7 @@ def WebIDLTest(parser, harness):
 
       [Exposed=Foo]
       interface Iface2 {
-        void method3();
+        undefined method3();
       };
     """)
     results = parser.finish()
@@ -87,12 +87,12 @@ def WebIDLTest(parser, harness):
 
       [Exposed=Foo]
       interface Iface3 {
-        void method4();
+        undefined method4();
       };
 
       [Exposed=(Foo,Bar1)]
       interface mixin Mixin {
-        void method5();
+        undefined method5();
       };
 
       Iface3 includes Mixin;
@@ -152,7 +152,7 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface Bar {
               [Exposed=Foo]
-              void operation();
+              undefined operation();
             };
         """)
 
@@ -188,7 +188,7 @@ def WebIDLTest(parser, harness):
             [Exposed=Foo]
             interface Baz {
               [Exposed=Bar]
-              void method();
+              undefined method();
             };
         """)
 
@@ -205,12 +205,12 @@ def WebIDLTest(parser, harness):
 
         [Exposed=Foo]
         interface Baz {
-          void method();
+          undefined method();
         };
 
         [Exposed=Bar]
         interface mixin Mixin {
-          void otherMethod();
+          undefined otherMethod();
         };
 
         Baz includes Mixin;
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_extended_attributes.py b/components/script/dom/bindings/codegen/parser/tests/test_extended_attributes.py
index 144c945bc10..66909f322c2 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_extended_attributes.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_extended_attributes.py
@@ -48,8 +48,8 @@ def WebIDLTest(parser, harness):
     parser = parser.reset()
     parser.parse("""
         interface TestClamp {
-          void testClamp([Clamp] long foo);
-          void testNotClamp(long foo);
+          undefined testClamp([Clamp] long foo);
+          undefined testNotClamp(long foo);
         };
     """)
 
@@ -66,7 +66,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface TestClamp2 {
-              void testClamp([Clamp=something] long foo);
+              undefined testClamp([Clamp=something] long foo);
             };
         """)
         results = parser.finish()
@@ -78,8 +78,8 @@ def WebIDLTest(parser, harness):
     parser = parser.reset()
     parser.parse("""
         interface TestEnforceRange {
-          void testEnforceRange([EnforceRange] long foo);
-          void testNotEnforceRange(long foo);
+          undefined testEnforceRange([EnforceRange] long foo);
+          undefined testNotEnforceRange(long foo);
         };
     """)
 
@@ -96,7 +96,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface TestEnforceRange2 {
-              void testEnforceRange([EnforceRange=something] long foo);
+              undefined testEnforceRange([EnforceRange=something] long foo);
             };
         """)
         results = parser.finish()
@@ -104,4 +104,4 @@ def WebIDLTest(parser, harness):
         threw = True
 
     harness.ok(threw, "[EnforceRange] must take no arguments")
-    
+
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 b7325cf9d26..8fbe9394042 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
@@ -14,23 +14,23 @@ def WebIDLTest(parser, harness):
           [LenientFloat]
           attribute double ld;
 
-          void m1(float arg1, double arg2, float? arg3, double? arg4,
+          undefined m1(float arg1, double arg2, float? arg3, double? arg4,
                   myFloat arg5, unrestricted float arg6,
                   unrestricted double arg7, unrestricted float? arg8,
                   unrestricted double? arg9, myUnrestrictedFloat arg10);
           [LenientFloat]
-          void m2(float arg1, double arg2, float? arg3, double? arg4,
+          undefined m2(float arg1, double arg2, float? arg3, double? arg4,
                   myFloat arg5, unrestricted float arg6,
                   unrestricted double arg7, unrestricted float? arg8,
                   unrestricted double? arg9, myUnrestrictedFloat arg10);
           [LenientFloat]
-          void m3(float arg);
+          undefined m3(float arg);
           [LenientFloat]
-          void m4(double arg);
+          undefined m4(double arg);
           [LenientFloat]
-          void m5((float or FloatTypes) arg);
+          undefined m5((float or FloatTypes) arg);
           [LenientFloat]
-          void m6(sequence<float> arg);
+          undefined m6(sequence<float> arg);
         };
     """)
 
@@ -70,7 +70,7 @@ def WebIDLTest(parser, harness):
         """)
     except Exception as x:
         threw = True
-    harness.ok(threw, "[LenientFloat] only allowed on void methods")
+    harness.ok(threw, "[LenientFloat] only allowed on undefined-retuning methods")
 
     parser = parser.reset()
     threw = False
@@ -78,7 +78,7 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface FloatTypes {
               [LenientFloat]
-              void m(unrestricted float arg);
+              undefined m(unrestricted float arg);
             };
         """)
     except Exception as x:
@@ -91,7 +91,7 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface FloatTypes {
               [LenientFloat]
-              void m(sequence<unrestricted float> arg);
+              undefined m(sequence<unrestricted float> arg);
             };
         """)
     except Exception as x:
@@ -104,7 +104,7 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface FloatTypes {
               [LenientFloat]
-              void m((unrestricted float or FloatTypes) arg);
+              undefined m((unrestricted float or FloatTypes) arg);
             };
         """)
     except Exception as x:
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_global_extended_attr.py b/components/script/dom/bindings/codegen/parser/tests/test_global_extended_attr.py
index 28b79642d86..3958f8ce104 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_global_extended_attr.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_global_extended_attr.py
@@ -22,7 +22,7 @@ def WebIDLTest(parser, harness):
           [Global, Exposed=Foo]
           interface Foo {
             getter any(DOMString name);
-            setter void(DOMString name, any arg);
+            setter undefined(DOMString name, any arg);
           };
         """)
         results = parser.finish()
@@ -40,7 +40,7 @@ def WebIDLTest(parser, harness):
           [Global, Exposed=Foo]
           interface Foo {
             getter any(DOMString name);
-            deleter void(DOMString name);
+            deleter undefined(DOMString name);
           };
         """)
         results = parser.finish()
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_incomplete_parent.py b/components/script/dom/bindings/codegen/parser/tests/test_incomplete_parent.py
index 1f520a28e16..8f30c212d7b 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_incomplete_parent.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_incomplete_parent.py
@@ -3,7 +3,7 @@ import WebIDL
 def WebIDLTest(parser, harness):
     parser.parse("""
         interface TestIncompleteParent : NotYetDefined {
-          void foo();
+          undefined foo();
         };
 
         interface NotYetDefined : EvenHigherOnTheChain {
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 47db3ae4cc9..a10bcd9863d 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_interface.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_interface.py
@@ -32,7 +32,7 @@ def WebIDLTest(parser, harness):
 
         interface QNameDerived : QNameBase {
           attribute long long foo;
-          attribute byte bar;          
+          attribute byte bar;
         };
     """)
     results = parser.finish()
@@ -99,11 +99,11 @@ def WebIDLTest(parser, harness):
             constructor();
             constructor(long arg);
             readonly attribute boolean x;
-            void foo();
+            undefined foo();
         };
         partial interface A {
             readonly attribute boolean y;
-            void foo(long arg);
+            undefined foo(long arg);
         };
     """);
     results = parser.finish();
@@ -127,13 +127,13 @@ def WebIDLTest(parser, harness):
     parser.parse("""
         partial interface A {
             readonly attribute boolean y;
-            void foo(long arg);
+            undefined foo(long arg);
         };
         interface A {
             constructor();
             constructor(long arg);
             readonly attribute boolean x;
-            void foo();
+            undefined foo();
         };
     """);
     results = parser.finish();
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 e070adee7e6..835212d2965 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
@@ -358,7 +358,7 @@ def WebIDLTest(parser, harness):
                        interface Foo1 {
                        %s;
                        [Throws]
-                       void %s(long test1, double test2, double test3);
+                       undefined %s(long test1, double test2, double test3);
                        };
                        """ % (likeMember, conflictName), expectedMembers)
         else:
@@ -367,14 +367,14 @@ def WebIDLTest(parser, harness):
                        interface Foo1 {
                        %s;
                        [Throws]
-                       void %s(long test1, double test2, double test3);
+                       undefined %s(long test1, double test2, double test3);
                        };
                        """ % (likeMember, conflictName))
         # Inherited conflicting methods should ALWAYS fail
         shouldFail("Conflicting inherited method: %s and %s" % (likeMember, conflictName),
                    """
                    interface Foo1 {
-                   void %s(long test1, double test2, double test3);
+                   undefined %s(long test1, double test2, double test3);
                    };
                    interface Foo2 : Foo1 {
                    %s;
@@ -384,7 +384,7 @@ def WebIDLTest(parser, harness):
                    """
                    interface Foo1 {
                    %s;
-                   static void %s(long test1, double test2, double test3);
+                   static undefined %s(long test1, double test2, double test3);
                    };
                    """ % (likeMember, conflictName))
         shouldFail("Conflicting attribute: %s and %s" % (likeMember, conflictName),
@@ -426,7 +426,7 @@ def WebIDLTest(parser, harness):
                maplike<long, long>;
                };
                interface Foo2 : Foo1 {
-               void entries();
+               undefined entries();
                };
                """, mapRWMembers, numProductions=2)
 
@@ -438,7 +438,7 @@ def WebIDLTest(parser, harness):
                interface Foo2 : Foo1 {
                };
                interface Foo3 : Foo2 {
-               void entries();
+               undefined entries();
                };
                """, mapRWMembers, numProductions=3)
 
@@ -448,7 +448,7 @@ def WebIDLTest(parser, harness):
                maplike<long, long>;
                };
                interface mixin Foo2 {
-               void entries();
+               undefined entries();
                };
                Foo1 includes Foo2;
                """)
@@ -459,7 +459,7 @@ def WebIDLTest(parser, harness):
                maplike<long, long>;
                };
                interface mixin Foo2 {
-               void entries();
+               undefined entries();
                };
                interface Foo3 : Foo1 {
                };
@@ -469,7 +469,7 @@ def WebIDLTest(parser, harness):
     shouldFail("Inheritance of name collision with child maplike/setlike",
                """
                interface Foo1 {
-               void entries();
+               undefined entries();
                };
                interface Foo2 : Foo1 {
                maplike<long, long>;
@@ -479,7 +479,7 @@ def WebIDLTest(parser, harness):
     shouldFail("Inheritance of multi-level name collision with child maplike/setlike",
                """
                interface Foo1 {
-               void entries();
+               undefined entries();
                };
                interface Foo2 : Foo1 {
                };
@@ -558,7 +558,7 @@ def WebIDLTest(parser, harness):
                maplike<long, long>;
                };
                interface Foo2 : Foo1 {
-               void clear();
+               undefined clear();
                };
                """, mapRWMembers, numProductions=2)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_interfacemixin.py b/components/script/dom/bindings/codegen/parser/tests/test_interfacemixin.py
index 477a9f37799..79cf1f6780d 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_interfacemixin.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_interfacemixin.py
@@ -30,11 +30,11 @@ def WebIDLTest(parser, harness):
     parser.parse("""
         interface mixin A {
             readonly attribute boolean x;
-            void foo();
+            undefined foo();
         };
         partial interface mixin A {
             readonly attribute boolean y;
-            void foo(long arg);
+            undefined foo(long arg);
         };
     """)
     results = parser.finish()
@@ -56,11 +56,11 @@ def WebIDLTest(parser, harness):
     parser.parse("""
         partial interface mixin A {
             readonly attribute boolean y;
-            void foo(long arg);
+            undefined foo(long arg);
         };
         interface mixin A {
             readonly attribute boolean x;
-            void foo();
+            undefined foo();
         };
     """)
     results = parser.finish()
@@ -212,7 +212,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface mixin A {
-                setter void (DOMString propertyName, double propertyValue);
+                setter undefined (DOMString propertyName, double propertyValue);
             };
         """)
         results = parser.finish()
@@ -226,7 +226,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface mixin A {
-                deleter void (DOMString propertyName);
+                deleter undefined (DOMString propertyName);
             };
         """)
         results = parser.finish()
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 88ee874386c..ff1f087c861 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_method.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_method.py
@@ -3,17 +3,17 @@ import WebIDL
 def WebIDLTest(parser, harness):
     parser.parse("""
         interface TestMethods {
-          void basic();
-          static void basicStatic();
-          void basicWithSimpleArgs(boolean arg1, byte arg2, unsigned long arg3);
+          undefined basic();
+          static undefined basicStatic();
+          undefined basicWithSimpleArgs(boolean arg1, byte arg2, unsigned long arg3);
           boolean basicBoolean();
           static boolean basicStaticBoolean();
           boolean basicBooleanWithSimpleArgs(boolean arg1, byte arg2, unsigned long arg3);
-          void optionalArg(optional byte? arg1, optional sequence<byte> arg2);
-          void variadicArg(byte?... arg1);
+          undefined optionalArg(optional byte? arg1, optional sequence<byte> arg2);
+          undefined variadicArg(byte?... arg1);
           object getObject();
-          void setObject(object arg1);
-          void setAny(any arg1);
+          undefined setObject(object arg1);
+          undefined setAny(any arg1);
           float doFloats(float arg1);
         };
     """)
@@ -70,12 +70,12 @@ def WebIDLTest(parser, harness):
                 (QName, name, type, optional, variadic) = expectedArgs[i]
                 checkArgument(gotArgs[i], QName, name, type, optional, variadic)
 
-    checkMethod(methods[0], "::TestMethods::basic", "basic", [("Void", [])])
+    checkMethod(methods[0], "::TestMethods::basic", "basic", [("Undefined", [])])
     checkMethod(methods[1], "::TestMethods::basicStatic", "basicStatic",
-                [("Void", [])], static=True)
+                [("Undefined", [])], static=True)
     checkMethod(methods[2], "::TestMethods::basicWithSimpleArgs",
                 "basicWithSimpleArgs",
-       [("Void",
+       [("Undefined",
         [("::TestMethods::basicWithSimpleArgs::arg1", "arg1", "Boolean", False, False),
          ("::TestMethods::basicWithSimpleArgs::arg2", "arg2", "Byte", False, False),
          ("::TestMethods::basicWithSimpleArgs::arg3", "arg3", "UnsignedLong", False, False)])])
@@ -89,22 +89,22 @@ def WebIDLTest(parser, harness):
          ("::TestMethods::basicBooleanWithSimpleArgs::arg3", "arg3", "UnsignedLong", False, False)])])
     checkMethod(methods[6], "::TestMethods::optionalArg",
                 "optionalArg",
-       [("Void",
+       [("Undefined",
         [("::TestMethods::optionalArg::arg1", "arg1", "ByteOrNull", True, False),
          ("::TestMethods::optionalArg::arg2", "arg2", "ByteSequence", True, False)])])
     checkMethod(methods[7], "::TestMethods::variadicArg",
                 "variadicArg",
-       [("Void",
+       [("Undefined",
         [("::TestMethods::variadicArg::arg1", "arg1", "ByteOrNull", True, True)])])
     checkMethod(methods[8], "::TestMethods::getObject",
                 "getObject", [("Object", [])])
     checkMethod(methods[9], "::TestMethods::setObject",
                 "setObject",
-       [("Void",
+       [("Undefined",
         [("::TestMethods::setObject::arg1", "arg1", "Object", False, False)])])
     checkMethod(methods[10], "::TestMethods::setAny",
                 "setAny",
-       [("Void",
+       [("Undefined",
         [("::TestMethods::setAny::arg1", "arg1", "Any", False, False)])])
     checkMethod(methods[11], "::TestMethods::doFloats",
                 "doFloats",
@@ -116,7 +116,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
           interface A {
-            void foo(optional float bar = 1);
+            undefined foo(optional float bar = 1);
           };
         """)
         results = parser.finish()
@@ -129,7 +129,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
           interface A {
-            [GetterThrows] void foo();
+            [GetterThrows] undefined foo();
           };
         """)
         results = parser.finish()
@@ -142,7 +142,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
           interface A {
-            [SetterThrows] void foo();
+            [SetterThrows] undefined foo();
           };
         """)
         results = parser.finish()
@@ -155,7 +155,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
           interface A {
-            [Throw] void foo();
+            [Throw] undefined foo();
           };
         """)
         results = parser.finish()
@@ -168,7 +168,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
           interface A {
-            void __noSuchMethod__();
+            undefined __noSuchMethod__();
           };
         """)
         results = parser.finish()
@@ -182,9 +182,9 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface A {
             [Throws, LenientFloat]
-            void foo(float myFloat);
+            undefined foo(float myFloat);
             [Throws]
-            void foo();
+            undefined foo();
           };
         """)
         results = parser.finish()
@@ -196,9 +196,9 @@ def WebIDLTest(parser, harness):
     parser.parse("""
       interface A {
         [Throws]
-        void foo();
+        undefined foo();
         [Throws, LenientFloat]
-        void foo(float myFloat);
+        undefined foo(float myFloat);
       };
     """)
     results = parser.finish()
@@ -213,9 +213,9 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface A {
             [Throws, LenientFloat]
-            void foo(float myFloat);
+            undefined foo(float myFloat);
             [Throws]
-            void foo(float myFloat, float yourFloat);
+            undefined foo(float myFloat, float yourFloat);
           };
         """)
         results = parser.finish()
@@ -229,9 +229,9 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface A {
             [Throws]
-            void foo(float myFloat, float yourFloat);
+            undefined foo(float myFloat, float yourFloat);
             [Throws, LenientFloat]
-            void foo(float myFloat);
+            undefined foo(float myFloat);
           };
         """)
         results = parser.finish()
@@ -245,9 +245,9 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           interface A {
             [Throws, LenientFloat]
-            void foo(float myFloat);
+            undefined foo(float myFloat);
             [Throws, LenientFloat]
-            void foo(short myShort);
+            undefined foo(short myShort);
           };
         """)
         results = parser.finish()
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_nullable_void.py b/components/script/dom/bindings/codegen/parser/tests/test_nullable_void.py
index 961ff825e9f..ebf841a5205 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_nullable_void.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_nullable_void.py
@@ -2,8 +2,8 @@ def WebIDLTest(parser, harness):
     threw = False
     try:
         parser.parse("""
-            interface NullableVoid {
-              void? foo();
+            interface NullableUndefined {
+              undefined? foo();
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_optional_constraints.py b/components/script/dom/bindings/codegen/parser/tests/test_optional_constraints.py
index 6217465ce7d..ad012b633d5 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_optional_constraints.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_optional_constraints.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface OptionalConstraints1 {
-              void foo(optional byte arg1, byte arg2);
+              undefined foo(optional byte arg1, byte arg2);
             };
         """)
 
@@ -18,7 +18,7 @@ def WebIDLTest(parser, harness):
     parser = parser.reset()
     parser.parse("""
         interface OptionalConstraints2 {
-          void foo(optional byte arg1 = 1, optional byte arg2 = 2,
+          undefined foo(optional byte arg1 = 1, optional byte arg2 = 2,
                    optional byte arg3, optional byte arg4 = 4,
                    optional byte arg5, optional byte arg6 = 9);
         };
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_overload.py b/components/script/dom/bindings/codegen/parser/tests/test_overload.py
index 3c680ad5233..8e02f64d6c9 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_overload.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_overload.py
@@ -3,16 +3,16 @@ import WebIDL
 def WebIDLTest(parser, harness):
     parser.parse("""
         interface TestOverloads {
-          void basic();
-          void basic(long arg1);
+          undefined basic();
+          undefined basic(long arg1);
           boolean abitharder(TestOverloads foo);
           boolean abitharder(boolean foo);
-          void abitharder(ArrayBuffer? foo);
-          void withVariadics(long... numbers);
-          void withVariadics(TestOverloads iface);
-          void withVariadics(long num, TestOverloads iface);
-          void optionalTest();
-          void optionalTest(optional long num1, long num2);
+          undefined abitharder(ArrayBuffer? foo);
+          undefined withVariadics(long... numbers);
+          undefined withVariadics(TestOverloads iface);
+          undefined withVariadics(long num, TestOverloads iface);
+          undefined optionalTest();
+          undefined optionalTest(optional long num1, long num2);
         };
     """)
 
@@ -37,11 +37,11 @@ def WebIDLTest(parser, harness):
 
     (retval, argumentSet) = signatures[0]
 
-    harness.check(str(retval), "Void", "Expect a void retval")
+    harness.check(str(retval), "Undefined", "Expect a undefined retval")
     harness.check(len(argumentSet), 0, "Expect an empty argument set")
 
     (retval, argumentSet) = signatures[1]
-    harness.check(str(retval), "Void", "Expect a void retval")
+    harness.check(str(retval), "Undefined", "Expect a undefined retval")
     harness.check(len(argumentSet), 1, "Expect an argument set with one argument")
 
     argument = argumentSet[0]
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_promise.py b/components/script/dom/bindings/codegen/parser/tests/test_promise.py
index 43c74029dc5..ef44a216d10 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_promise.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_promise.py
@@ -64,7 +64,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface A {
-              void foo(Promise<any>? arg);
+              undefined foo(Promise<any>? arg);
             };
         """)
         results = parser.finish();
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 d50572caf07..3d83e249be8 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_record.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_record.py
@@ -4,7 +4,7 @@ def WebIDLTest(parser, harness):
     parser.parse("""
         dictionary Dict {};
         interface RecordArg {
-          void foo(record<DOMString, Dict> arg);
+          undefined foo(record<DOMString, Dict> arg);
         };
     """)
 
@@ -27,16 +27,16 @@ def WebIDLTest(parser, harness):
     threw = False
     try:
         parser.parse("""
-            interface RecordVoidArg {
-              void foo(record<DOMString, void> arg);
+            interface RecordUndefinedArg {
+              undefined foo(record<DOMString, undefined> arg);
             };
         """)
 
         results = parser.finish()
     except Exception as x:
         threw = True
-    harness.ok(threw, "Should have thrown because record can't have void as value type.")
- 
+    harness.ok(threw, "Should have thrown because record can't have undefined as value type.")
+
     parser = parser.reset()
     threw = False
     try:
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_securecontext_extended_attribute.py b/components/script/dom/bindings/codegen/parser/tests/test_securecontext_extended_attribute.py
index 442dba45d76..5af0c22803c 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_securecontext_extended_attribute.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_securecontext_extended_attribute.py
@@ -6,12 +6,12 @@ def WebIDLTest(parser, harness):
         interface TestSecureContextOnInterface {
           const octet TEST_CONSTANT = 0;
           readonly attribute byte testAttribute;
-          void testMethod(byte foo);
+          undefined testMethod(byte foo);
         };
         partial interface TestSecureContextOnInterface {
           const octet TEST_CONSTANT_2 = 0;
           readonly attribute byte testAttribute2;
-          void testMethod2(byte foo);
+          undefined testMethod2(byte foo);
         };
     """)
     results = parser.finish()
@@ -37,13 +37,13 @@ def WebIDLTest(parser, harness):
         partial interface TestSecureContextOnInterfaceAfterPartialInterface {
           const octet TEST_CONSTANT_2 = 0;
           readonly attribute byte testAttribute2;
-          void testMethod2(byte foo);
+          undefined testMethod2(byte foo);
         };
         [SecureContext]
         interface TestSecureContextOnInterfaceAfterPartialInterface {
           const octet TEST_CONSTANT = 0;
           readonly attribute byte testAttribute;
-          void testMethod(byte foo);
+          undefined testMethod(byte foo);
         };
      """)
     results = parser.finish()
@@ -68,13 +68,13 @@ def WebIDLTest(parser, harness):
         interface TestSecureContextOnPartialInterface {
           const octet TEST_CONSTANT = 0;
           readonly attribute byte testAttribute;
-          void testMethod(byte foo);
+          undefined testMethod(byte foo);
         };
         [SecureContext]
         partial interface TestSecureContextOnPartialInterface {
           const octet TEST_CONSTANT_2 = 0;
           readonly attribute byte testAttribute2;
-          void testMethod2(byte foo);
+          undefined testMethod2(byte foo);
         };
     """)
     results = parser.finish()
@@ -105,10 +105,10 @@ def WebIDLTest(parser, harness):
           [SecureContext]
           readonly attribute byte testSecureAttribute;
           readonly attribute byte testNonSecureAttribute2;
-          void testNonSecureMethod1(byte foo);
+          undefined testNonSecureMethod1(byte foo);
           [SecureContext]
-          void testSecureMethod(byte foo);
-          void testNonSecureMethod2(byte foo);
+          undefined testSecureMethod(byte foo);
+          undefined testNonSecureMethod2(byte foo);
         };
     """)
     results = parser.finish()
@@ -147,10 +147,10 @@ def WebIDLTest(parser, harness):
           [SecureContext]
           readonly attribute byte testSecureAttribute;
           readonly attribute byte testNonSecureAttribute2;
-          void testNonSecureMethod1(byte foo);
+          undefined testNonSecureMethod1(byte foo);
           [SecureContext]
-          void testSecureMethod(byte foo);
-          void testNonSecureMethod2(byte foo);
+          undefined testSecureMethod(byte foo);
+          undefined testNonSecureMethod2(byte foo);
         };
     """)
     results = parser.finish()
@@ -194,10 +194,10 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface TestSecureContextForOverloads1 {
               [SecureContext]
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
             partial interface TestSecureContextForOverloads1 {
-              void testSecureMethod(byte foo, byte bar);
+              undefined testSecureMethod(byte foo, byte bar);
             };
         """)
         results = parser.finish()
@@ -211,11 +211,11 @@ def WebIDLTest(parser, harness):
         parser.parse("""
             interface TestSecureContextForOverloads2 {
               [SecureContext]
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
             partial interface TestSecureContextForOverloads2 {
               [SecureContext]
-              void testSecureMethod(byte foo, byte bar);
+              undefined testSecureMethod(byte foo, byte bar);
             };
         """)
         results = parser.finish()
@@ -230,7 +230,7 @@ def WebIDLTest(parser, harness):
             [SecureContext]
             interface TestSecureContextOnInterfaceAndMember {
               [SecureContext]
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
         """)
         results = parser.finish()
@@ -247,7 +247,7 @@ def WebIDLTest(parser, harness):
             [SecureContext]
             partial interface TestSecureContextOnPartialInterfaceAndMember {
               [SecureContext]
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
         """)
         results = parser.finish()
@@ -264,7 +264,7 @@ def WebIDLTest(parser, harness):
             };
             partial interface TestSecureContextOnInterfaceAndPartialInterfaceMember {
               [SecureContext]
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
         """)
         results = parser.finish()
@@ -280,7 +280,7 @@ def WebIDLTest(parser, harness):
             interface TestSecureContextOnInheritedInterface {
             };
             interface TestSecureContextNotOnInheritingInterface : TestSecureContextOnInheritedInterface {
-              void testSecureMethod(byte foo);
+              undefined testSecureMethod(byte foo);
             };
         """)
         results = parser.finish()
@@ -298,7 +298,7 @@ def WebIDLTest(parser, harness):
         interface mixin TestNonSecureContextMixin {
           const octet TEST_CONSTANT_2 = 0;
           readonly attribute byte testAttribute2;
-          void testMethod2(byte foo);
+          undefined testMethod2(byte foo);
         };
         TestSecureContextInterfaceThatIncludesNonSecureContextMixin includes TestNonSecureContextMixin;
      """)
@@ -314,13 +314,13 @@ def WebIDLTest(parser, harness):
                "Attributes copied from non-[SecureContext] mixin should not be [SecureContext]")
     harness.ok(results[0].members[3].getExtendedAttribute("SecureContext") is None,
                "Methods copied from non-[SecureContext] mixin should not be [SecureContext]")
- 
+
     # Test SecureContext and NoInterfaceObject
     parser = parser.reset()
     parser.parse("""
         [NoInterfaceObject, SecureContext]
         interface TestSecureContextNoInterfaceObject {
-          void testSecureMethod(byte foo);
+          undefined testSecureMethod(byte foo);
         };
     """)
     results = parser.finish()
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_special_method_signature_mismatch.py b/components/script/dom/bindings/codegen/parser/tests/test_special_method_signature_mismatch.py
index 52cfcb96817..b209c850d6b 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_special_method_signature_mismatch.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_special_method_signature_mismatch.py
@@ -17,7 +17,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface SpecialMethodSignatureMismatch2 {
-              getter void foo(unsigned long index);
+              getter undefined foo(unsigned long index);
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_special_methods.py b/components/script/dom/bindings/codegen/parser/tests/test_special_methods.py
index 7f911733b62..c657c9c797d 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_special_methods.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_special_methods.py
@@ -61,7 +61,7 @@ def WebIDLTest(parser, harness):
         parser.parse(
             """
             interface IndexedDeleter {
-              deleter void(unsigned long index);
+              deleter undefined(unsigned long index);
             };
             """)
         parser.finish()
@@ -69,5 +69,5 @@ def WebIDLTest(parser, harness):
         threw = True
 
     harness.ok(threw, "There are no indexed deleters")
-        
-        
+
+
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 b5fc1c68890..d98088380ba 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_typedef.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_typedef.py
@@ -4,9 +4,9 @@ def WebIDLTest(parser, harness):
       typedef long? mynullablelong;
       interface Foo {
         const mylong X = 5;
-        void foo(optional mynullablelong arg = 7);
-        void bar(optional mynullablelong arg = null);
-        void baz(mylong arg);
+        undefined foo(optional mynullablelong arg = 7);
+        undefined bar(optional mynullablelong arg = null);
+        undefined baz(mylong arg);
       };
     """)
 
@@ -21,7 +21,7 @@ def WebIDLTest(parser, harness):
         parser.parse("""
           typedef long? mynullablelong;
           interface Foo {
-            void foo(mynullablelong? Y);
+            undefined foo(mynullablelong? Y);
           };
         """)
         results = parser.finish()
@@ -44,7 +44,7 @@ def WebIDLTest(parser, harness):
         threw = True
 
     harness.ok(threw, "Should have thrown on nullable inside nullable const.")
-    
+
     parser = parser.reset()
     threw = False
     try:
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 770a9d3736f..e72548f637f 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_unforgeable.py
@@ -47,7 +47,7 @@ def WebIDLTest(parser, harness):
     parser = parser.reset();
     parser.parse("""
             interface Child : Parent {
-              static void foo();
+              static undefined foo();
             };
             interface Parent {
               [Unforgeable] readonly attribute long foo;
@@ -65,7 +65,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Child : Parent {
-              void foo();
+              undefined foo();
             };
             interface Parent {
               [Unforgeable] readonly attribute long foo;
@@ -84,10 +84,10 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Child : Parent {
-              void foo();
+              undefined foo();
             };
             interface Parent {
-              [Unforgeable] void foo();
+              [Unforgeable] undefined foo();
             };
         """)
 
@@ -125,7 +125,7 @@ def WebIDLTest(parser, harness):
               attribute short foo;
             };
             interface Parent {
-              [Unforgeable] void foo();
+              [Unforgeable] undefined foo();
             };
         """)
 
@@ -157,7 +157,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface Child : Parent {
-              void foo();
+              undefined foo();
             };
             interface Parent {};
             interface mixin Mixin {
@@ -187,7 +187,7 @@ def WebIDLTest(parser, harness):
             };
             GrandParent includes Mixin;
             interface mixin ChildMixin {
-              void foo();
+              undefined foo();
             };
             Child includes ChildMixin;
         """)
@@ -209,11 +209,11 @@ def WebIDLTest(parser, harness):
             interface Parent : GrandParent {};
             interface GrandParent {};
             interface mixin Mixin {
-              [Unforgeable] void foo();
+              [Unforgeable] undefined foo();
             };
             GrandParent includes Mixin;
             interface mixin ChildMixin {
-              void foo();
+              undefined foo();
             };
             Child includes ChildMixin;
         """)
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 801314fd0bd..469208b264d 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_union.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_union.py
@@ -136,10 +136,10 @@ def WebIDLTest(parser, harness):
         """
     for (i, type) in enumerate(validUnionTypes):
         interface += string.Template("""
-          void method${i}(${type} arg);
+          undefined method${i}(${type} arg);
           ${type} returnMethod${i}();
           attribute ${type} attr${i};
-          void optionalMethod${i}(${type}? arg);
+          undefined optionalMethod${i}(${type}? arg);
         """).substitute(i=i, type=type)
     interface += """
         };
@@ -152,7 +152,7 @@ def WebIDLTest(parser, harness):
     for invalid in invalidUnionTypes:
         interface = testPre + string.Template("""
             interface TestUnion {
-              void method(${type} arg);
+              undefined method(${type} arg);
             };
         """).substitute(type=invalid)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_union_any.py b/components/script/dom/bindings/codegen/parser/tests/test_union_any.py
index e34cadab470..3eb67648d56 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_union_any.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_union_any.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface AnyNotInUnion {
-              void foo((any or DOMString) arg);
+              undefined foo((any or DOMString) arg);
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_union_nullable.py b/components/script/dom/bindings/codegen/parser/tests/test_union_nullable.py
index 08430a94a2e..71da4349e6e 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_union_nullable.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_union_nullable.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface OneNullableInUnion {
-              void foo((object? or DOMString?) arg);
+              undefined foo((object? or DOMString?) arg);
             };
         """)
 
@@ -20,7 +20,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface NullableInNullableUnion {
-              void foo((object? or DOMString)? arg);
+              undefined foo((object? or DOMString)? arg);
             };
         """)
 
@@ -40,7 +40,7 @@ def WebIDLTest(parser, harness):
             interface NullableInUnionNullableUnionHelper {
             };
             interface NullableInUnionNullableUnion {
-              void foo(((object? or DOMString) or NullableInUnionNullableUnionHelper)? arg);
+              undefined foo(((object? or DOMString) or NullableInUnionNullableUnionHelper)? arg);
             };
         """)
 
diff --git a/components/script/dom/bindings/codegen/parser/tests/test_variadic_constraints.py b/components/script/dom/bindings/codegen/parser/tests/test_variadic_constraints.py
index 7448e40d5a9..e36eff8b476 100644
--- a/components/script/dom/bindings/codegen/parser/tests/test_variadic_constraints.py
+++ b/components/script/dom/bindings/codegen/parser/tests/test_variadic_constraints.py
@@ -3,7 +3,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface VariadicConstraints1 {
-              void foo(byte... arg1, byte arg2);
+              undefined foo(byte... arg1, byte arg2);
             };
         """)
         results = parser.finish()
@@ -20,7 +20,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface VariadicConstraints2 {
-              void foo(byte... arg1, optional byte arg2);
+              undefined foo(byte... arg1, optional byte arg2);
             };
         """)
         results = parser.finish();
@@ -36,7 +36,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface VariadicConstraints3 {
-              void foo(optional byte... arg1);
+              undefined foo(optional byte... arg1);
             };
         """)
         results = parser.finish()
@@ -53,7 +53,7 @@ def WebIDLTest(parser, harness):
     try:
         parser.parse("""
             interface VariadicConstraints4 {
-              void foo(byte... arg1 = 0);
+              undefined foo(byte... arg1 = 0);
             };
         """)
         results = parser.finish()