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 092eece9ac5f427e7bf33a1913c3ae1f5dd9c4b4..dba8f3a032c0c70f05d0960d0c2c48f1d85c3f41 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -219,13 +219,16 @@ public:
     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();
 
+    // For OfflineAudioContext-specific tasks.
+    virtual bool shouldSuspendNow();
+    virtual void resolvePendingSuspendPromises();
+
     // 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.
@@ -238,11 +241,16 @@ public:
     // Get the security origin for this audio context.
     SecurityOrigin* securityOrigin() const;
 
+    Member<AudioBuffer> renderTarget() const { return m_renderTarget; }
+    AudioDestinationNode* destination() const { return m_destinationNode; }
+
 protected:
     explicit AudioContext(Document*);
     AudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
 
-    RefPtrWillBeMember<ScriptPromiseResolver> m_offlineResolver;
+    // Shared with OfflineAudioContext.
+    void setContextState(AudioContextState);
+
 private:
     void initialize();
     void uninitialize();
@@ -307,7 +315,6 @@ private:
 
     // The state of the AudioContext.
     AudioContextState m_contextState;
-    void setContextState(AudioContextState);
 
     AsyncAudioDecoder m_audioDecoder;