Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AbstractAudioContext.cpp

Index: Source/modules/webaudio/AbstractAudioContext.cpp
diff --git a/Source/modules/webaudio/AbstractAudioContext.cpp b/Source/modules/webaudio/AbstractAudioContext.cpp
index 16484cab1bbdcd0bd9cf3bbb75a5a323e88afecc..39ca7a0e5a3f468a97b0c56a7b4009c11802415b 100644
--- a/Source/modules/webaudio/AbstractAudioContext.cpp
+++ b/Source/modules/webaudio/AbstractAudioContext.cpp
@@ -693,10 +693,38 @@ void AbstractAudioContext::handleStoppableSourceNodes()
     }
 }
 
+void AbstractAudioContext::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 AbstractAudioContext::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.
+    //
+    // Also note that we do not need to run resolvePromiseForResume() here
+    // because the offline audio context keeps its own suspend/resume promise
+    // resolvers separately.
+    if (!hasRealtimeConstraint()) {
+        deferredTaskHandler().offlineContextLock();
+        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()) {
@@ -715,19 +743,20 @@ void AbstractAudioContext::handlePostRenderTasks()
 {
     ASSERT(isAudioThread());
 
+    // Same as |handlePreRenderTasks()|. We force to perform the post-render
+    // tasks for the offline rendering.
+    if (!hasRealtimeConstraint()) {
+        deferredTaskHandler().offlineContextLock();
+        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();
     }
 }
@@ -800,33 +829,8 @@ void AbstractAudioContext::startRendering()
     }
 }
 
-void AbstractAudioContext::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(renderedBuffer);
-    if (!renderedBuffer)
-        return;
-
-    // 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);
-    }
-}
-
 DEFINE_TRACE(AbstractAudioContext)
 {
-    visitor->trace(m_offlineResolver);
     visitor->trace(m_renderTarget);
     visitor->trace(m_destinationNode);
     visitor->trace(m_listener);