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..0d823ee2e21151b095784c5a51720a7a75d4414e 100644
--- a/Source/modules/webaudio/OfflineAudioContext.h
+++ b/Source/modules/webaudio/OfflineAudioContext.h
@@ -36,12 +36,43 @@ class MODULES_EXPORT OfflineAudioContext final : public AudioContext {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static OfflineAudioContext* create(ExecutionContext*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate, ExceptionState&);
-
     virtual ~OfflineAudioContext();
 
+    virtual bool suspendIfNecessary();
+    bool isSuspendScheduled() const;
+
     ScriptPromise startOfflineRendering(ScriptState*);
+    ScriptPromise suspendOfflineRendering(ScriptState*, double suspendTime);
+    ScriptPromise resumeOfflineRendering(ScriptState*);
+
 private:
     OfflineAudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
+
+    // A container class for pairs of time information and suspend promise.
+    class ScheduledSuspendContainer : public NoBaseWillBeGarbageCollected<ScheduledSuspendContainer> {
+    public:
+        static PassOwnPtr<ScheduledSuspendContainer> create(double, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+        ~ScheduledSuspendContainer();
+        PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver() { return m_resolver; }
+        bool shouldBeSuspendedNow(double currentTime) const;

[Raymond Toy, 2015/05/19 22:04:45]

Add comment on what this is supposed to do.

[hongchan, 2015/05/20 22:09:41]

Done.

+
+        DECLARE_TRACE();
+
+    private:
+        ScheduledSuspendContainer(double, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+
+        double m_when;
+        RefPtrWillBeMember<ScriptPromiseResolver> m_resolver;
+    };
+
+    void suspendAndResolveOnMainThread(unsigned);
+
+    // Unlike the design of real-time audio context, we keep suspend/resume

[Raymond Toy, 2015/05/19 22:04:45]

This comment is wrong now since we're not using just one. Online context only
has a list for resume.

+    // promises in separate two vectors. This is because suspend() accompanies
+    // the timing information whereas resume() resolves when it is actually
+    // called.
+    WillBeHeapVector<OwnPtrWillBeMember<ScheduledSuspendContainer>> m_scheduledSuspends;
+    WillBeHeapVector<RefPtrWillBeMember<ScriptPromiseResolver>> m_resumeResolvers;
 };
 
 } // namespace blink