Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AbstractAudioContext.h

Index: Source/modules/webaudio/AbstractAudioContext.h
diff --git a/Source/modules/webaudio/AbstractAudioContext.h b/Source/modules/webaudio/AbstractAudioContext.h
index 5994c223ef747ca2a9a8fd28584233c983c62d91..ce0fbb09234f8f0c5938fa433ab3b80966eaaf07 100644
--- a/Source/modules/webaudio/AbstractAudioContext.h
+++ b/Source/modules/webaudio/AbstractAudioContext.h
@@ -160,8 +160,13 @@ public:
     // Close
     virtual ScriptPromise closeContext(ScriptState*) = 0;
 
-    // Suspend/Resume
+    // Suspend for online audio context.
     virtual ScriptPromise suspendContext(ScriptState*) = 0;
+
+    // Suspend for offline audio context.
+    virtual ScriptPromise suspendContext(ScriptState*, double) = 0;
+
+    // Resume
     virtual ScriptPromise resumeContext(ScriptState*) = 0;
 
     // When a source node has started processing and needs to be protected,
@@ -220,13 +225,14 @@ public:
     const AtomicString& interfaceName() const final;
     ExecutionContext* executionContext() const final;
 
-    DEFINE_ATTRIBUTE_EVENT_LISTENER(complete);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
     void startRendering();
-    void fireCompletionEvent();
     void notifyStateChange();
 
+    // TODO(hongchan): move this to OfflineAudioContext.
+    AudioBuffer* renderTarget() const { return m_renderTarget.get(); }
+
     // A context is considered closed if:
     //  - closeContext() has been called.
     //  - it has been stopped by its execution context.
@@ -243,8 +249,6 @@ protected:
     virtual void didClose() {}
     void uninitialize();
 
-    RefPtrWillBeMember<ScriptPromiseResolver> m_offlineResolver;
-
     // FIXME(dominicc): Move m_resumeResolvers to AudioContext, because only
     // it creates these Promises.
     // Vector of promises created by resume(). It takes time to handle them, so we collect all of
@@ -300,6 +304,8 @@ private:
     bool m_didInitializeContextGraphMutex;
     RefPtr<DeferredTaskHandler> m_deferredTaskHandler;
 
+    // For offline audio context.
+    // TODO(hongchan): move this to OfflineAudioContext class.
     Member<AudioBuffer> m_renderTarget;
 
     // The state of the AbstractAudioContext.
@@ -312,6 +318,9 @@ private:
     // can, try to stop them so they can be collected.
     void handleStoppableSourceNodes();
 
+    // Perform common tasks after the render quantum. Called by handlePostRenderTasks().
+    void performPostRenderTasks();
+
     // This is considering 32 is large enough for multiple channels audio.
     // It is somewhat arbitrary and could be increased if necessary.
     enum { MaxNumberOfChannels = 32 };