Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioDestinationNode.h

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 #ifndef OfflineAudioDestinationNode_h
 #define OfflineAudioDestinationNode_h
 
 #include "modules/webaudio/AudioBuffer.h"
+#include "modules/webaudio/AudioContext.h"
 #include "modules/webaudio/AudioDestinationNode.h"
+#include "modules/webaudio/OfflineAudioContext.h"
 #include "public/platform/WebThread.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class AudioBus;
 class AudioContext;
+class OfflineAudioContext;
 
 class OfflineAudioDestinationHandler final : public AudioDestinationHandler {
 public:
     static PassRefPtr<OfflineAudioDestinationHandler> create(AudioNode&, AudioBuffer* renderTarget);
     virtual ~OfflineAudioDestinationHandler();
 
     // AudioHandler
     virtual void dispose() override;
     virtual void initialize() override;
     virtual void uninitialize() override;
 
     // AudioDestinationHandler
     virtual void startRendering() override;
     virtual void stopRendering() override;
 
     virtual float sampleRate()  const override { return m_renderTarget->sampleRate(); }
 
 private:
     OfflineAudioDestinationHandler(AudioNode&, AudioBuffer* renderTarget);
-    void offlineRender();
-    void offlineRenderInternal();
 
-    // For completion callback on main thread.
+    // For start/suspend/resume rendering.
+    void initiateOfflineRendering();
+    void renderNextQuantum();
+    void finishOfflineRendering();
+
+    // For callback on main thread.
+    void notifySuspend();
     void notifyComplete();
 
-    // This AudioHandler renders into this AudioBuffer.
-    // This Persistent doesn't make a reference cycle including the owner
-    // OfflineAudioDestinationNode.
+    // This AudioHandler renders into this AudioBuffer. This Persistent doesn't
+    // make a reference cycle including the owner OfflineAudioDestinationNode.
     Persistent<AudioBuffer> m_renderTarget;
+
     // Temporary AudioBus for each render quantum.
     RefPtr<AudioBus> m_renderBus;
 
     // Rendering thread.
     OwnPtr<WebThread> m_renderThread;
-    bool m_startedRendering;

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

Changed the name?  Why?

+
+    bool m_isRenderingStarted;
+
+    unsigned m_framesProcessed;
+    size_t m_framesToProcess;

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

Why is m_framesProcessed unsigned but m_framesToProcess size_t?

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

I just followed the previous implementation. Should I change?

[Raymond Toy, 2015/05/19 21:46:40]

IIUC, m_framesProcessed counts up from 0 to the length of the offline context. 
If so, I think it should be the same type as m_framesToProcess which seems to
count down from the the offline context length.

[hongchan, 2015/05/20 22:09:40]

Done.

 };
 
 class OfflineAudioDestinationNode final : public AudioDestinationNode {
 public:
     static OfflineAudioDestinationNode* create(AudioContext*, AudioBuffer* renderTarget);
 
 private:
     OfflineAudioDestinationNode(AudioContext&, AudioBuffer* renderTarget);
 };
 
 } // namespace blink
 
 #endif // OfflineAudioDestinationNode_h