Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioContext.h

Index: Source/modules/webaudio/AudioContext.h
diff --git a/Source/modules/webaudio/AudioContext.h b/Source/modules/webaudio/AudioContext.h
index 5b19a40d2b8248048d972429ba0e5fe3275e7b52..f8753ef417f1587594967940eb5aedc6a6e163d8 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -220,9 +220,13 @@ public:
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
     void startRendering();
-    void fireCompletionEvent();
     void notifyStateChange();
 
+    // From offline rendering.
+    void fireSuspendEvent();
+    void fireCompletionEvent();
+    virtual bool suspendIfNecessary();
+
     // A context is considered closed if:
     //  - closeContext() has been called, even if the audio HW has not yet been
     //    stopped.  It will be stopped eventually.
@@ -240,6 +244,14 @@ protected:
     AudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
 
     RefPtrWillBeMember<ScriptPromiseResolver> m_offlineResolver;
+    Member<AudioDestinationNode> m_destinationNode;
+    bool m_didInitializeContextGraphMutex;
+    Member<AudioBuffer> m_renderTarget;
+
+    // The state of the AudioContext.
+    void setContextState(AudioContextState);
+    AudioContextState m_contextState;
+
 private:
     void initialize();
     void uninitialize();
@@ -259,7 +271,7 @@ private:
     // haven't finished playing.  Make sure to release them here.
     void releaseActiveSourceNodes();
 
-    Member<AudioDestinationNode> m_destinationNode;

[Raymond Toy, 2015/05/13 17:16:08]

Try not to move things around.  It makes it hard to figure out what changed and
this particular one looks like m_destinationNode was removed, but it was just
moved above.

[hongchan, 2015/05/13 17:30:53]

Yes, this relocation was not necessary. However, there are things need to be
moved because of the order of initializers. Some methods and variables should be
accessed by OAC so they need to be in the protected state (from the private).

This is just work-in-progress artifacts. Will be cleaned up.

+
     Member<AudioListener> m_listener;
 
     // Only accessed in the audio thread.
@@ -299,18 +311,10 @@ private:
 
     unsigned m_connectionCount;
 
-    // Graph locking.
-    bool m_didInitializeContextGraphMutex;
     RefPtr<DeferredTaskHandler> m_deferredTaskHandler;
 
-    Member<AudioBuffer> m_renderTarget;
-
     bool m_isOfflineContext;
 
-    // The state of the AudioContext.
-    AudioContextState m_contextState;
-    void setContextState(AudioContextState);
-
     AsyncAudioDecoder m_audioDecoder;
 
     // The Promise that is returned by close();