Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioContext.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 201 matching lines @@
 #endif
     using AutoLocker = DeferredTaskHandler::AutoLocker;
 
     // Returns the maximum numuber of channels we can support.
     static unsigned maxNumberOfChannels() { return MaxNumberOfChannels;}
 
     // EventTarget
     virtual const AtomicString& interfaceName() const override final;
     virtual ExecutionContext* executionContext() const override final;
 
-    DEFINE_ATTRIBUTE_EVENT_LISTENER(complete);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
     void startRendering();
-    void fireCompletionEvent();
+    virtual void fireCompletionEvent();
     void notifyStateChange();
+    virtual bool shouldSuspendNow();

[Raymond Toy, 2015/05/28 16:37:35]

Isn't this only used by an offline context?

[hongchan, 2015/06/09 20:49:59]

This is used by OfflineAudioDestinatioNode. That's why I made it public.

[Raymond Toy, 2015/06/09 22:34:59]

Then why not make it a private method in OfflineAudioDestinationNode?

 
     // 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.
     //  - it has been stopped (or is stopping) by its execution context.
     bool isContextClosed() const { return m_closeResolver || m_isStopScheduled || m_isCleared; }
 
     static unsigned s_hardwareContextCount;
     static unsigned s_contextId;
 
     // Get the security origin for this audio context.
     SecurityOrigin* securityOrigin() const;
 
 protected:
     explicit AudioContext(Document*);
     AudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
 
-    RefPtrWillBeMember<ScriptPromiseResolver> m_offlineResolver;
+    // Shared with OfflineAudioContext.
+    void setContextState(AudioContextState);
+    bool m_didInitializeContextGraphMutex;
+    bool m_isOfflineContext;
+    Member<AudioBuffer> m_renderTarget;
+    Member<AudioDestinationNode> m_destinationNode;

[Raymond Toy, 2015/05/28 16:37:35]

I think an offline context should use destination() to get this, so this member
variable doesn't need to be protected.  Maybe we should also add
isOfflineContext() method and renderTarget() method?

[hongchan, 2015/06/09 20:49:59]

Seems like a good idea. Will look into it.

+
 private:
     void initialize();
     void uninitialize();
 
     // ExecutionContext calls stop twice.
     // We'd like to schedule only one stop action for them.
     bool m_isStopScheduled;
     bool m_isCleared;
     void clear();
 
     void throwExceptionForClosedState(ExceptionState&);
 
     // Set to true when the destination node has been initialized and is ready to process data.
     bool m_isInitialized;
 
     // When the context goes away, there might still be some sources which
     // haven't finished playing.  Make sure to release them here.
     void releaseActiveSourceNodes();
 
-    Member<AudioDestinationNode> m_destinationNode;
     Member<AudioListener> m_listener;
 
     // Only accessed in the audio thread.
     // These raw pointers are safe because AudioSourceNodes in
     // m_activeSourceNodes own them.
     Vector<AudioHandler*> m_finishedSourceHandlers;
 
     // List of source nodes. This is either accessed when the graph lock is
     // held, or on the main thread when the audio thread has finished.
     // Oilpan: This Vector holds connection references. We must call
@@ skipping 14 matching lines @@
     WillBeHeapVector<RefPtrWillBeMember<ScriptPromiseResolver>> m_resumeResolvers;
     void rejectPendingResolvers();
 
     // True if we're in the process of resolving promises for resume().  Resolving can take some
     // time and the audio context process loop is very fast, so we don't want to call resolve an
     // excessive number of times.
     bool m_isResolvingResumePromises;
 
     unsigned m_connectionCount;
 
-    // Graph locking.

[Raymond Toy, 2015/05/28 16:37:35]

Preserve these comments with the variable that you moved.  Also line 308.

[hongchan, 2015/06/09 20:49:59]

Will do!

-    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();
     RefPtrWillBeMember<ScriptPromiseResolver> m_closeResolver;
 
     // Tries to handle AudioBufferSourceNodes that were started but became disconnected or was never
     // connected. Because these never get pulled anymore, they will stay around forever. So if we
     // can, try to stop them so they can be collected.
     void handleStoppableSourceNodes();
 
     // This is considering 32 is large enough for multiple channels audio.
     // It is somewhat arbitrary and could be increased if necessary.
     enum { MaxNumberOfChannels = 32 };
 
     unsigned m_contextId;
 };
 
 } // namespace blink
 
 #endif // AudioContext_h