Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/DeferredTaskHandler.h

 /*
  * Copyright (C) 2010, 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 90 matching lines @@
     ThreadIdentifier audioThread() const { return acquireLoad(&m_audioThread); }
 
     // TODO(hongchan): Use no-barrier load here. (crbug.com/247328)
     //
     // It is okay to use a relaxed (no-barrier) load here. Because the data
     // referenced by m_audioThread is not actually being used, thus we do not
     // need a barrier between the load of m_audioThread and of that data.
     bool isAudioThread() const { return currentThread() == acquireLoad(&m_audioThread); }
 
     void lock();
+
+    // This allows the regular lock in offline audio rendering. It is okay to
+    // lock the offline audio render thread because it is not real-time thread.

[Raymond Toy, 2015/07/17 15:44:03]

Nit: Add comment this must only be used for offline contexts.

[hongchan, 2015/07/17 15:51:17]

Done.

+    void offlineContextLock();
+
     bool tryLock();
     void unlock();
+
 #if ENABLE(ASSERT)
     // Returns true if this thread owns the context's lock.
     bool isGraphOwner();
 #endif
 
     class MODULES_EXPORT AutoLocker {
         STACK_ALLOCATED();
     public:
         explicit AutoLocker(DeferredTaskHandler& handler)
             : m_handler(handler)
@@ skipping 42 matching lines @@
     Vector<RefPtr<AudioHandler>> m_deletableOrphanHandlers;
 
     // Graph locking.
     RecursiveMutex m_contextGraphMutex;
     volatile ThreadIdentifier m_audioThread;
 };
 
 } // namespace blink
 
 #endif // DeferredTaskHandler_h