Add a script to update the WebIDL parser.

src/components/script/dom/bindings/codegen/parser/external.patch

@@ -0,0 +1,49 @@
+--- WebIDL.py
++++ WebIDL.py
+@@ -450,44 +450,8 @@ class IDLIdentifierPlaceholder(IDLObjectWithIdentifier):
+ 
+ class IDLExternalInterface(IDLObjectWithIdentifier):
+     def __init__(self, location, parentScope, identifier):
+-        assert isinstance(identifier, IDLUnresolvedIdentifier)
+-        assert isinstance(parentScope, IDLScope)
+-        self.parent = None
+-        IDLObjectWithIdentifier.__init__(self, location, parentScope, identifier)
+-        IDLObjectWithIdentifier.resolve(self, parentScope)
+-
+-    def finish(self, scope):
+-        pass
+-
+-    def validate(self):
+-        pass
+-
+-    def isExternal(self):
+-        return True
+-
+-    def isInterface(self):
+-        return True
+-
+-    def isConsequential(self):
+-        return False
+-
+-    def addExtendedAttributes(self, attrs):
+-        assert len(attrs) == 0
+-
+-    def resolve(self, parentScope):
+-        pass
+-
+-    def getJSImplementation(self):
+-        return None
+-
+-    def isJSImplemented(self):
+-        return False
+-
+-    def getNavigatorProperty(self):
+-        return None
+-
+-    def _getDependentObjects(self):
+-        return set()
++        raise WebIDLError("Servo does not support external interfaces.",
++                          [self.location])
+ 
+ class IDLPartialInterface(IDLObject):
+     def __init__(self, location, name, members, nonPartialInterface):