Remove Webkit prefix for RequestAnimationFrame.

lib/html/scripts/systemnative.py

Index: lib/html/scripts/systemnative.py
===================================================================
--- lib/html/scripts/systemnative.py	(revision 12808)
+++ lib/html/scripts/systemnative.py	(working copy)
@@ -11,6 +11,10 @@
 import systembase
 from generator import *
 
+_dart_custom_members = set([
+    'Window.webkitCancelAnimationFrame',
+    'Window.webkitRequestAnimationFrame',
+    ])
 
 class NativeImplementationSystem(systembase.System):
 
@@ -542,12 +546,19 @@
     self._GenerateNativeBinding('numericIndexSetter', 3, dart_declaration,
         'Callback', True)
 
+  def _HasCustomImplementation(self, member_name):
+    member_name = '%s.%s' % (self._html_interface_name, member_name)
+    return member_name in _dart_custom_members
+
   def AddOperation(self, info, html_name):
     """
     Arguments:
       info: An OperationInfo object.
     """
 
+    if self._HasCustomImplementation(info.name):
+      return
+
     operation = info.operations[0]
 
     if 'CheckSecurityForNode' in operation.ext_attrs: