[dartium] Use ScriptWrappable when there are multiple Dart wrappers.

Source/bindings/dart/custom/DartWindowCustom.cpp

 // Copyright 2011, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * Redistributions in binary form must reproduce the above
@@ skipping 57 matching lines @@
     // FIXME: proper implementation.
     DART_UNIMPLEMENTED();
 }
 
 void historyCrossFrameGetter(Dart_NativeArguments args)
 {
     {
         DOMWindow* receiver = DartDOMWrapper::receiver<DOMWindow>(args);
         DartDOMData* domData = static_cast<DartDOMData*>(Dart_GetNativeIsolateData(args));
 
+        Dart_WeakPersistentHandle existingWrapper = DartDOMWrapper::lookupWrapper<DartHistory>(domData, &receiver->history());
+        if (existingWrapper) {
+            Dart_SetWeakHandleReturnValue(args, existingWrapper);
+            return;
+        }
+
         Dart_Handle result = DartDOMWrapper::createWrapper<DartHistory>(
             domData, &receiver->history(), _HistoryCrossFrameClassId);
         if (result)
             Dart_SetReturnValue(args, result);
     }
 }
 
 void locationCrossFrameGetter(Dart_NativeArguments args)
 {
     {
         DOMWindow* receiver = DartDOMWrapper::receiver<DOMWindow>(args);
         DartDOMData* domData = static_cast<DartDOMData*>(Dart_GetNativeIsolateData(args));
 
+        Dart_WeakPersistentHandle existingWrapper = DartDOMWrapper::lookupWrapper<DartLocation>(domData, &receiver->location());
+        if (existingWrapper) {
+            Dart_SetWeakHandleReturnValue(args, existingWrapper);
+            return;
+        }
+
         Dart_Handle result = DartDOMWrapper::createWrapper<DartLocation>(
             domData, &receiver->location(), _LocationCrossFrameClassId);
         if (result)
             Dart_SetReturnValue(args, result);
     }
 }
 
 void locationSetter(Dart_NativeArguments args)
 {
     Dart_Handle exception = 0;
@@ skipping 223 matching lines @@
 
 }
 
 Dart_Handle DartWindow::createWrapper(DartDOMData* domData, DOMWindow* window)
 {
     return DartDOMWrapper::createWrapper<DartWindow>(
         domData, window, _DOMWindowCrossFrameClassId);
 }
 
 }