Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioDestinationNode.h

Index: Source/modules/webaudio/OfflineAudioDestinationNode.h
diff --git a/Source/modules/webaudio/OfflineAudioDestinationNode.h b/Source/modules/webaudio/OfflineAudioDestinationNode.h
index ca70d96aa1f5974f2f96f337040ff40479475c2d..1d91d73c564ccb58b7869444393407956e2dac54 100644
--- a/Source/modules/webaudio/OfflineAudioDestinationNode.h
+++ b/Source/modules/webaudio/OfflineAudioDestinationNode.h
@@ -26,7 +26,9 @@
 #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"
@@ -35,6 +37,7 @@ namespace blink {
 
 class AudioBus;
 class AudioContext;
+class OfflineAudioContext;
 
 class OfflineAudioDestinationHandler final : public AudioDestinationHandler {
 public:
@@ -54,22 +57,30 @@ public:
 
 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;
+
+    bool m_isRenderingStarted;
+
+    unsigned m_framesProcessed;
+    size_t m_framesToProcess;
 };
 
 class OfflineAudioDestinationNode final : public AudioDestinationNode {