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

Source/WebCore/bindings/dart/DartIsolate.h

 // Copyright 2012, 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 18 matching lines @@
 
 #ifndef DartIsolate_h
 #define DartIsolate_h
 
 #include <dart_api.h>
 #include <wtf/RefPtr.h>
 #include <wtf/ThreadSafeRefCounted.h>
 
 namespace WebCore {
 
-class DartEventListener;
-
 class DartIsolate : public ThreadSafeRefCounted<DartIsolate> {
     WTF_MAKE_NONCOPYABLE(DartIsolate);
 public:
     static PassRefPtr<DartIsolate> create(Dart_Isolate isolate)
     {
         return adoptRef(new DartIsolate(isolate));
     }
 
     ~DartIsolate();
 
@@ skipping 27 matching lines @@
     private:
         RefPtr<DartIsolate> m_isolate;
     };
 
 private:
     DartIsolate(Dart_Isolate);
 
     Dart_Isolate m_isolate;
 };
 
-
-
 }
 
 #endif // DartIsolate_h