Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioContext.h

Index: Source/modules/webaudio/OfflineAudioContext.h
diff --git a/Source/modules/webaudio/OfflineAudioContext.h b/Source/modules/webaudio/OfflineAudioContext.h
index 99276e7cbb5e19dc7edf2934b67a726f2eed8d2a..d545a6358863a137acda008e17fec15877bb2b9a 100644
--- a/Source/modules/webaudio/OfflineAudioContext.h
+++ b/Source/modules/webaudio/OfflineAudioContext.h
@@ -36,12 +36,63 @@ class MODULES_EXPORT OfflineAudioContext final : public AudioContext {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static OfflineAudioContext* create(ExecutionContext*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate, ExceptionState&);
-
     virtual ~OfflineAudioContext();
 
+    // Check all the scheduled suspends if the context should suspend at
+    // currentTime(). Then post tasks to resolve promises on the main thread
+    // if necessary.
+    virtual bool shouldSuspendNow();
+
+    // Fire completion event when the rendering is finished.
+    virtual void fireCompletionEvent();
+
+    DEFINE_ATTRIBUTE_EVENT_LISTENER(complete);
+
     ScriptPromise startOfflineRendering(ScriptState*);
+    ScriptPromise suspendOfflineRendering(ScriptState*, double);
+    ScriptPromise resumeOfflineRendering(ScriptState*);
+
 private:
     OfflineAudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
+
+    // A container class for a pair of time information and the suspend promise
+    // resolver.
+    class ScheduledSuspendContainer
+    : public NoBaseWillBeGarbageCollected<ScheduledSuspendContainer> {
+    public:
+        static PassOwnPtr<ScheduledSuspendContainer> create(size_t, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);

[Raymond Toy, 2015/05/28 16:37:36]

I think adding an argument variable for size_t would be useful.

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

Done.

+        ~ScheduledSuspendContainer();
+        PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver() { return m_resolver; }
+
+        bool shouldSuspendAt(size_t) const;

[Raymond Toy, 2015/05/28 16:37:36]

Add parameter name for size_t.

[hongchan, 2015/06/09 20:50:00]

Done.

+
+        DECLARE_TRACE();
+
+    private:
+        ScheduledSuspendContainer(size_t, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);

[Raymond Toy, 2015/05/28 16:37:36]

Add parameter name for size_t.

[hongchan, 2015/06/09 20:50:00]

Done.

+
+        // Specified suspend time in samples and associated promise resolver.

[Raymond Toy, 2015/05/28 16:37:36]

This comment looks like it applies to m_when, which doesn't make sense. 
Simplify and move the last part to a new comment for m_resolver.

[hongchan, 2015/06/09 20:50:00]

Done.

+        size_t m_when;

[Raymond Toy, 2015/05/28 16:37:36]

"when" is used for time (in sec) everywhere else.  Maybe rename this to mention
frame or rendering quantum or something to show that it's not in sec.

[hongchan, 2015/06/09 20:50:00]

I used m_whenAsFrame once, but thought it was too long. Will think about it.

+        RefPtrWillBeMember<ScriptPromiseResolver> m_resolver;
+    };
+
+    // Resolve a suspend at the given index in the scheduled suspend list. This
+    // changes the state of context and then remove the promise from the list.

[Raymond Toy, 2015/05/28 16:37:36]

"remove" -> "removes"

[hongchan, 2015/06/09 20:50:00]

Done.

+    void resolveSuspendOnMainThread(unsigned);
+
+    // Check if there are scheduled suspends with the same frame.
+    bool isValidToScheduleAt(size_t);

[Raymond Toy, 2015/05/28 16:37:36]

Add parameter name.

[hongchan, 2015/06/09 20:50:00]

Done.

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

Where did isValidToScheduleAt go to?

+
+    WillBeHeapVector<OwnPtrWillBeMember<ScheduledSuspendContainer>> m_scheduledSuspends;
+    RefPtrWillBeMember<ScriptPromiseResolver> m_completeResolver;
+
+    // This flag is necessary to indicate the rendering has actually started.
+    // Note that initial state of context is 'Suspended', which is the same
+    // state when the context is suspended.
+    bool m_isRenderingStarted;
+
+    // Total render sample length.
+    size_t m_totalRenderFrames;
 };
 
 } // namespace blink