DOM wrappers that are not retained from Dart should be collected.

Source/WebCore/bindings/dart/DartController.h

 // 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 62 matching lines @@
 
     Dart_Handle spawnDomIsolate(DOMWindow* targetWindow, const String& entryPoint);
 
     static DartController* retrieve(Frame*);
     static DartController* retrieve(ScriptExecutionContext*);
 
 private:
     static void initVMIfNeeded();
 
     static PassRefPtr<DartIsolate> createIsolate(Document*, PassRefPtr<DartApplicationLoader>);
-    static void shutdownIsolate(DartIsolate* isolate);
 
     static bool createPureIsolateCallback(const char* prefix, void*, char** errorMsg);
     void installDartExtensions(v8::Handle<v8::Context>);
 
     bool isDartMimeType(const String& mimeType);
     void loadScripts();
 
     void didLeaveScriptContext(int recursion);
 
     // The frame that owns this controller.
     Frame* m_frame;
 
     bool m_scriptsLoaded;
 
     // Isolates associated with scripts in this document.
     Vector< RefPtr<DartIsolate> > m_isolates;
 
     typedef HashMap<String, NPObject*> NPObjectMap;
     NPObjectMap m_npObjectMap;
 
     friend class DartIsolate;
     friend class DartScriptRunner;
 };
 
 }
 
 #endif // DartController_h