Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/DeferredTaskHandler.h

Index: Source/modules/webaudio/DeferredTaskHandler.h
diff --git a/Source/modules/webaudio/DeferredTaskHandler.h b/Source/modules/webaudio/DeferredTaskHandler.h
index b145642b82ea96eb3bd9de6e5d1ab3f3de8955c8..3e3c7b3d0c4643b60b1d66f81b386f850085ccb4 100644
--- a/Source/modules/webaudio/DeferredTaskHandler.h
+++ b/Source/modules/webaudio/DeferredTaskHandler.h
@@ -108,8 +108,14 @@ public:
     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();