Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioContext.cpp

Index: Source/modules/webaudio/AudioContext.cpp
diff --git a/Source/modules/webaudio/AudioContext.cpp b/Source/modules/webaudio/AudioContext.cpp
index a6e0aebbeeab2c4dc1278d17ec43f392fd25f5df..099432faf44f8a419214f959cd69b4ec37a3d6e6 100644
--- a/Source/modules/webaudio/AudioContext.cpp
+++ b/Source/modules/webaudio/AudioContext.cpp
@@ -730,15 +730,9 @@ void AudioContext::notifyStateChange()
 ScriptPromise AudioContext::suspendContext(ScriptState* scriptState)
 {
     ASSERT(isMainThread());
-    AutoLocker locker(this);
+    ASSERT(!isOfflineContext());
 
-    if (isOfflineContext()) {
-        return ScriptPromise::rejectWithDOMException(
-            scriptState,
-            DOMException::create(
-                InvalidAccessError,
-                "cannot suspend an OfflineAudioContext"));
-    }
+    AutoLocker locker(this);
 
     RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
@@ -848,10 +842,34 @@ void AudioContext::handleStoppableSourceNodes()
     }
 }
 
+void AudioContext::performPostRenderTasks()
+{
+    // Take care of AudioNode tasks where the tryLock() failed previously.
+    deferredTaskHandler().breakConnections();
+
+    // Dynamically clean up nodes which are no longer needed.
+    releaseFinishedSourceNodes();
+
+    deferredTaskHandler().handleDeferredTasks();
+    deferredTaskHandler().requestToDeleteHandlersOnMainThread();
+}
+
 void AudioContext::handlePreRenderTasks()
 {
     ASSERT(isAudioThread());
 
+    // For the precise offline audio rendering, we need these tasks to be
+    // performed every render quantum. Thus, we wait for the graph lock (rather
+    // than tryLock()) so we can run the pre-render tasks without deferring
+    // them.
+    if (isOfflineContext()) {
+        deferredTaskHandler().forceLock();
+        deferredTaskHandler().handleDeferredTasks();
+        handleStoppableSourceNodes();
+        unlock();
+        return;
+    }
+
     // At the beginning of every render quantum, try to update the internal rendering graph state (from main thread changes).
     // It's OK if the tryLock() fails, we'll just take slightly longer to pick up the changes.
     if (tryLock()) {
@@ -870,19 +888,20 @@ void AudioContext::handlePostRenderTasks()
 {
     ASSERT(isAudioThread());
 
+    // Same as |handlePreRenderTasks()|. We force to perform the post-render
+    // tasks for the offline rendering.
+    if (isOfflineContext()) {
+        deferredTaskHandler().forceLock();
+        performPostRenderTasks();
+        unlock();
+        return;
+    }
+
     // Must use a tryLock() here too.  Don't worry, the lock will very rarely be contended and this method is called frequently.
     // The worst that can happen is that there will be some nodes which will take slightly longer than usual to be deleted or removed
     // from the render graph (in which case they'll render silence).
     if (tryLock()) {
-        // Take care of AudioNode tasks where the tryLock() failed previously.
-        deferredTaskHandler().breakConnections();
-
-        // Dynamically clean up nodes which are no longer needed.
-        releaseFinishedSourceNodes();
-
-        deferredTaskHandler().handleDeferredTasks();
-        deferredTaskHandler().requestToDeleteHandlersOnMainThread();
-
+        performPostRenderTasks();
         unlock();
     }
 }
@@ -945,9 +964,10 @@ ExecutionContext* AudioContext::executionContext() const
 
 void AudioContext::startRendering()
 {
-    // This is called for both online and offline contexts.
+    // This is only for the real-time context.
     ASSERT(isMainThread());
     ASSERT(m_destinationNode);
+    ASSERT(!isOfflineContext());
 
     if (m_contextState == Suspended) {
         destination()->audioDestinationHandler().startRendering();
@@ -970,32 +990,23 @@ void AudioContext::stopRendering()
 
 void AudioContext::fireCompletionEvent()
 {
-    ASSERT(isMainThread());
-    if (!isMainThread())
-        return;
-
-    AudioBuffer* renderedBuffer = m_renderTarget.get();
-
-    // For an offline context, we set the state to closed here so that the oncomplete handler sees
-    // that the context has been closed.
-    setContextState(Closed);
+    ASSERT_WITH_MESSAGE(1, "fireCompletionEvent() only valid for offline audio context");
+}
 
-    ASSERT(renderedBuffer);
-    if (!renderedBuffer)
-        return;
+bool AudioContext::shouldSuspendNow()
+{
+    ASSERT_WITH_MESSAGE(1, "shouldSuspendNow() only valid for offline audio context");
+    return false;
+}
 
-    // Avoid firing the event if the document has already gone away.
-    if (executionContext()) {
-        // Call the offline rendering completion event listener and resolve the promise too.
-        dispatchEvent(OfflineAudioCompletionEvent::create(renderedBuffer));
-        m_offlineResolver->resolve(renderedBuffer);
-    }
+void AudioContext::resolvePendingSuspendPromises()
+{
+    ASSERT_WITH_MESSAGE(1, "clearResolvedSuspend() only valid for offline audio context");
 }
 
 DEFINE_TRACE(AudioContext)
 {
     visitor->trace(m_closeResolver);
-    visitor->trace(m_offlineResolver);
     visitor->trace(m_renderTarget);
     visitor->trace(m_destinationNode);
     visitor->trace(m_listener);