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..abf9a8d7033956ac4efa98a3e8de05f76e38a7f3 100644
--- a/Source/modules/webaudio/OfflineAudioContext.h
+++ b/Source/modules/webaudio/OfflineAudioContext.h
@@ -27,10 +27,15 @@
 
 #include "modules/ModulesExport.h"
 #include "modules/webaudio/AudioContext.h"
+#include "wtf/HashMap.h"
 
 namespace blink {
 
 class ExceptionState;
+class ScheduledSuspendContainer;
+
+// The HashMap with 'zero' key is needed because |currentSampleFrame| can be zero.
+using SuspendContainerMap = HashMap<size_t, RefPtr<ScheduledSuspendContainer>, DefaultHash<size_t>::Hash, WTF::UnsignedWithZeroKeyHashTraits<size_t>>;
 
 class MODULES_EXPORT OfflineAudioContext final : public AudioContext {
     DEFINE_WRAPPERTYPEINFO();
@@ -39,9 +44,81 @@ public:
 
     virtual ~OfflineAudioContext();
 
+    DECLARE_VIRTUAL_TRACE();
+
+    // Fire completion event when the rendering is finished.
+    void fireCompletionEvent() override;
+
+    // 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() override;
+
+    // Clear suspensions marked as 'resolved' in the list.
+    void resolvePendingSuspendPromises() override;
+
+    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);
+
+    // Check if there is any duplicate entry in scheduled suspends and reject
+    // the promise if needed.
+    void checkDuplicateSuspend(PassRefPtr<ScheduledSuspendContainer>);
+
+    // Reject a suspend promise on the main thread when the validation fails.
+    void rejectSuspendPromiseOnMainThread(PassRefPtr<ScheduledSuspendContainer>);
+
+    // Resolve a pending suspend promise and removes it from the map.
+    void resolvePendingSuspendPromisesOnMainThread(PassRefPtr<ScheduledSuspendContainer>);
+
+    SuspendContainerMap 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;
+};
+
+// A container class for a pair of time information and the suspend promise
+// resolver.
+//
+// TODO: This class is |ThreadSafeRefCounted| because it needs to be accessed by
+// the offline render thread which is not oilpan-enabled. This is a short-term
+// solution until the offline render thread gets oilpan coverage.
+class ScheduledSuspendContainer : public ThreadSafeRefCounted<ScheduledSuspendContainer> {
+public:
+    static PassRefPtr<ScheduledSuspendContainer> create(double suspendTime, size_t suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+    ~ScheduledSuspendContainer();
+
+    PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver() { return m_resolver; }
+
+    double suspendTime() const { return m_suspendTime; }
+
+    size_t suspendFrame() const { return m_suspendFrame; }
+
+    // Query if the rendering should be suspended at |whenFrame|.
+    bool shouldSuspendAtFrame(size_t whenFrame) const;
+
+private:
+    ScheduledSuspendContainer(double suspendTime, size_t suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+
+    // Actual suspend time before the quantization by render quantum frame.
+    double m_suspendTime;
+
+    // Suspend sample frame. This is quantized by the render quantum size.
+    size_t m_suspendFrame;
+
+    // Associated promise resolver.
+    RefPtrWillBePersistent<ScriptPromiseResolver> m_resolver;
 };
 
 } // namespace blink