Tried using CrossThreadPersistent for workerDebuggerAgents

Source/core/inspector/InspectorCanvasAgent.cpp

 /*
  * 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 54 matching lines @@
     , m_injectedScriptManager(injectedScriptManager)
     , m_frontend(0)
     , m_enabled(false)
 {
 }
 
 InspectorCanvasAgent::~InspectorCanvasAgent()
 {
 }
 
+void InspectorCanvasAgent::trace(Visitor* visitor)
+{
+    visitor->trace(m_pageAgent);
+    InspectorBaseAgent::trace(visitor);
+}
+
 void InspectorCanvasAgent::setFrontend(InspectorFrontend* frontend)
 {
     ASSERT(frontend);
     m_frontend = frontend->canvas();
 }
 
 void InspectorCanvasAgent::clearFrontend()
 {
     m_frontend = 0;
     disable(0);
@@ skipping 256 matching lines @@
     ErrorString error;
     for (FramesWithUninstrumentedCanvases::const_iterator it = m_framesWithUninstrumentedCanvases.begin(); it != m_framesWithUninstrumentedCanvases.end(); ++it) {
         InjectedScriptCanvasModule module = injectedScriptCanvasModule(&error, ScriptState::forMainWorld(it->key));
         if (!module.isEmpty())
             module.markFrameEnd();
     }
 }
 
 } // namespace WebCore