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..7de70700dc0499d64c5e22f9baa82d23b2b2f0af 100644
--- a/Source/modules/webaudio/OfflineAudioContext.h
+++ b/Source/modules/webaudio/OfflineAudioContext.h
@@ -39,9 +39,73 @@ public:
 
     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.
+    bool shouldSuspendNow();
+
+    // Clear suspensions marked as 'resolved' in the list.
+    void resolvePendingSuspendPromises();
+
+    // Fire completion event when the rendering is finished.
+    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 suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+        ~ScheduledSuspendContainer();
+        PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver() { return m_resolver; }
+
+        // Query if the rendering should be suspended at |whenFrame|.
+        bool shouldSuspendAt(size_t whenFrame) const;
+
+        // Query if the suspend is pending for the promise resolution.
+        bool isPending() const;
+
+        // Mark the suspend as pending. Containers with 'pending' flag will
+        // be collectively resolved when the actual suspension happens.
+        void markAsPending();
+
+        DECLARE_TRACE();
+
+    private:
+        ScheduledSuspendContainer(size_t suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+
+        // Suspend time in samples.
+        size_t m_suspendFrame;
+
+        // Associated promise resolver.
+        RefPtrWillBeMember<ScriptPromiseResolver> m_resolver;
+
+        // A pending marker for the safe batch removal.
+        bool m_isPending;
+    };
+
+    // Resolve pending suspend promises and removes it from the list.
+    void resolvePendingSuspendPromisesOnMainThread();
+
+    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