Run microtasks at the end of each worker task.

Source/core/workers/WorkerThread.h

 /*
  * Copyright (C) 2008 Apple 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 98 matching lines @@
 
         void initialize();
         void cleanup();
         void idleHandler();
         void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
         bool m_terminated;
         OwnPtr<WorkerSharedTimer> m_sharedTimer;
         MessageQueue<WorkerThreadTask> m_debuggerMessageQueue;
         OwnPtr<PendingGCRunner> m_pendingGCRunner;
+        OwnPtr<WebThread::TaskObserver> m_microtaskRunner;
         OwnPtr<MessageLoopInterruptor> m_messageLoopInterruptor;
 
         WorkerLoaderProxy& m_workerLoaderProxy;
         WorkerReportingProxy& m_workerReportingProxy;
 
         RefPtrWillBePersistent<WorkerInspectorController> m_workerInspectorController;
         Mutex m_workerInspectorControllerMutex;
 
         Mutex m_threadCreationMutex;
         RefPtrWillBePersistent<WorkerGlobalScope> m_workerGlobalScope;
         OwnPtrWillBePersistent<WorkerThreadStartupData> m_startupData;
 
         // Used to signal thread shutdown.
         OwnPtr<blink::WebWaitableEvent> m_shutdownEvent;
 
         // FIXME: This has to be last because of crbug.com/401397 - the
         // WorkerThread might get deleted before it had a chance to properly
         // shut down. By deleting the WebThread first, we can guarantee that
         // no pending tasks on the thread might want to access any of the other
         // members during the WorkerThread's destruction.
         OwnPtr<blink::WebThread> m_thread;
     };
 
 } // namespace blink
 
 #endif // WorkerThread_h