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

Source/WebCore/bindings/dart/DartDOMData.h

 /*
  * Copyright (C) 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 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef DartDOMData_h
 #define DartDOMData_h
 
 #include <dart_api.h>
 #include <wtf/HashMap.h>
+#include <wtf/HashSet.h>
 #include <wtf/RefPtr.h>
 #include <wtf/Vector.h>
 
 namespace WebCore {
 
+class DOMWindow;
 class DartApplicationLoader;
 class DartEventListener;
 class ScriptExecutionContext;
-class DOMWindow;
+class WeakCallbackData;
 
 typedef HashMap<void*, Dart_Handle> DartDOMMap;
 typedef Vector< RefPtr<DartEventListener> > DartEventListenerList;
+typedef HashSet<DartWeakCallback*> DartWeakCallbacks;
 
 class DartDOMData {
 public:
     DartDOMData(PassRefPtr<DartApplicationLoader> applicationLoader, ScriptExecutionContext* context);
+    ~DartDOMData();
 
     PassRefPtr<DartApplicationLoader> applicationLoader();
     ScriptExecutionContext* scriptExecutionContext() { return m_scriptExecutionContext; }
     DOMWindow* domWindow() { return m_domWindow; }
     DartDOMMap* domMap() { return &m_domMap; }
     DartEventListenerList* eventListeners() { return &m_eventListeners; }
+    DartWeakCallbacks* weakCallbacks() { return &m_weakCallbacks; }
     int* recursion() { return &m_recursion; }
 
 private:
     RefPtr<DartApplicationLoader> m_applicationLoader;
     ScriptExecutionContext* m_scriptExecutionContext;
     DOMWindow* m_domWindow;
     DartDOMMap m_domMap;
     DartEventListenerList m_eventListeners;
+    DartWeakCallbacks m_weakCallbacks;
     int m_recursion;
 };
 
 }
 
 #endif // DartDOMData_h