Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/DeferredTaskHandler.cpp

 /*
  * 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 24 matching lines @@
 
 namespace blink {
 
 void DeferredTaskHandler::lock()
 {
     // Don't allow regular lock in real-time audio thread.
     ASSERT(isMainThread());
     m_contextGraphMutex.lock();
 }
 
+void DeferredTaskHandler::forceLock()
+{
+    // This allows the regular lock in non-real-time audio thread.
+    ASSERT(!isMainThread());
+    if (isMainThread()) {
+        // If this gets called in the main thread, do tryLock() instead.
+        m_contextGraphMutex.tryLock();

[haraken, 2015/06/17 06:46:08]

Two questions:

- This can fail. Is it OK?
- Why does the main thread need to use tryLock()? The main thread is not a
realtime thread.

[hongchan, 2015/06/17 20:10:39]

For this pattern, I would like to ask your opinion. I just want to be able to
lock the graph in the offline audio rendering. What would be the most
simple/elegant? Just lock() it?

+        return;
+    }
+
+    m_contextGraphMutex.lock();
+}
+
 bool DeferredTaskHandler::tryLock()
 {
     // Try to catch cases of using try lock on main thread
     // - it should use regular lock.
     ASSERT(isAudioThread());
     if (!isAudioThread()) {
         // In release build treat tryLock() as lock() (since above
         // ASSERT(isAudioThread) never fires) - this is the best we can do.
         lock();
         return true;
@@ skipping 212 matching lines @@
 {
     ASSERT(isMainThread());
     AutoLocker locker(*this);
     m_renderingOrphanHandlers.clear();
     m_deletableOrphanHandlers.clear();
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)