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

Source/WebCore/bindings/dart/DartUtilities.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 109 matching lines @@
     static int* recursionForIsolate(Dart_Isolate);
     static int* recursionForCurrentIsolate();
 
     static ScriptExecutionContext* scriptExecutionContext();
 
     static bool processingUserGesture();
 
     static PassRefPtr<ScriptArguments> createScriptArguments(Dart_Handle argument, Dart_Handle& exception);
     static PassRefPtr<ScriptCallStack> createScriptCallStack();
 
+    static Dart_Handle createWeakPersistentHandle(Dart_Handle object, void* peer, Dart_WeakPersistentHandleFinalizer);
+    static void disposeWeakPersistentHandles();
+
     static const uint8_t* fullSnapshot();
 
     static void reportProblem(ScriptExecutionContext*, Dart_Handle);
 
     static Dart_Handle invalidNumberOfArgumentsException()
     {
         return Dart_NewString("Invalid number of arguments");
     }
 
     static Dart_Handle conditionalFunctionalityException()
@@ skipping 20 matching lines @@
     DartApiScope() { Dart_EnterScope(); }
     ~DartApiScope() { Dart_ExitScope(); }
 };
 
 #define DART_UNIMPLEMENTED_EXCEPTION() DartUtilities::notImplementedException(__FILE__, __LINE__)
 #define DART_UNIMPLEMENTED() Dart_ThrowException(DART_UNIMPLEMENTED_EXCEPTION());
 
 } // namespace WebCore
 
 #endif // DartUtilities_h