Oilpan: Move MainThreadTaskRunner into Oilpan heap.

Source/core/dom/MainThreadTaskRunner.cpp

 /*
  * Copyright (C) 2013 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 56 matching lines @@
     , m_weakFactory(this)
     , m_pendingTasksTimer(this, &MainThreadTaskRunner::pendingTasksTimerFired)
     , m_suspended(false)
 {
 }
 
 MainThreadTaskRunner::~MainThreadTaskRunner()
 {
 }
 
+DEFINE_TRACE(MainThreadTaskRunner)
+{
+    visitor->trace(m_context);
+}
+
 void MainThreadTaskRunner::postTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task)
 {
     if (!task->taskNameForInstrumentation().isEmpty())
         InspectorInstrumentation::didPostExecutionContextTask(m_context, task.get());
     Platform::current()->mainThread()->postTask(location, new MainThreadTask(m_weakFactory.createWeakPtr(), task, false));
 }
 
 void MainThreadTaskRunner::postInspectorTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task)
 {
     Platform::current()->mainThread()->postTask(location, new MainThreadTask(m_weakFactory.createWeakPtr(), task, true));
@@ skipping 38 matching lines @@
         const bool instrumenting = !task->taskNameForInstrumentation().isEmpty();
         if (instrumenting)
             InspectorInstrumentation::willPerformExecutionContextTask(m_context, task.get());
         task->performTask(m_context);
         if (instrumenting)
             InspectorInstrumentation::didPerformExecutionContextTask(m_context);
     }
 }
 
 } // namespace