auto merge of #2101 : jdm/servo/newroot_rebase, r=Ms2ger

As described in #1764, this strategy uses the following properties:
* DOM members are `JS<T>` types. These cannot be used with being explicitly rooted, but they are required for compiler-derived trace hooks.
* Methods that take DOM type arguments receive `&[mut] JSRef<T>`. These are rooted value references that are cloneable but cannot escape.
* Methods that return DOM values use `Unrooted<T>`. These are values that may or may not be rooted elsewhere, but callers must root them in order to interact with them in any way. One unsoundness hole exists - `Unrooted` values must be rooted ASAP, or there exists the danger that JSAPI calls could be made that could cause the underlying JS value to be GCed.
* All methods are implemented on `JSRef<T>`, enforcing the requirement that all DOM values are rooted for the duration of a method call (with a few exceptions for layout-related code, which cannot root values and therefore interacts with `JS<T>` and `&T` values - this is safe under the assumption that layout code interacts with DOM nodes that are in the tree, therefore rooted, and does not run concurrently with content code)

1 files changed, 9 insertions, 4 deletions

diff --git a/src/components/script/dom/bindings/codegen/Configuration.py b/src/components/script/dom/bindings/codegen/Configuration.py
index a1ccb460ee2..1272867f542 100644
--- a/src/components/script/dom/bindings/codegen/Configuration.py
+++ b/src/components/script/dom/bindings/codegen/Configuration.py
@@ -128,14 +128,19 @@ class Descriptor(DescriptorProvider):
 
         # Read the desc, and fill in the relevant defaults.
         ifaceName = self.interface.identifier.name
+
+        # Callback types do not use JS smart pointers, so we should not use the
+        # built-in rooting mechanisms for them.
         if self.interface.isCallback():
-            nativeTypeDefault = "nsIDOM" + ifaceName
+            self.needsRooting = False
         else:
-            nativeTypeDefault = 'JS<%s>' % ifaceName
+            self.needsRooting = True
 
-        self.nativeType = desc.get('nativeType', nativeTypeDefault)
+        self.returnType = "Temporary<%s>" % ifaceName
+        self.argumentType = "JSRef<%s>" % ifaceName
+        self.memberType = "Root<'a, 'b, %s>" % ifaceName
+        self.nativeType = desc.get('nativeType', 'JS<%s>' % ifaceName)
         self.concreteType = desc.get('concreteType', ifaceName)
-        self.needsAbstract = desc.get('needsAbstract', [])
         self.createGlobal = desc.get('createGlobal', False)
         self.register = desc.get('register', True)
         self.outerObjectHook = desc.get('outerObjectHook', 'None')