Have the DeferredTaskHandler be the source of whether tail processing handlers can be added.

Bug: 884059
Change-Id: Iaee6daa6003c4956e6dba6d5351621b10bc0b5e1
Reviewed-on: https://chromium-review.googlesource.com/c/1332254Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608073}

third_party/blink/renderer/modules/webaudio/audio_node.cc

@@ -450,10 +450,9 @@ void AudioHandler::DisableOutputsIfNecessary() {
     // the outputs so that the tail for the node can be output.
     // Otherwise, we can disable the outputs right away.
     if (RequiresTailProcessing()) {
-      if (Context()->ContextState() !=
-          BaseAudioContext::AudioContextState::kClosed) {
-        Context()->GetDeferredTaskHandler().AddTailProcessingHandler(this);
-      }
+      auto& deferred_task_handler = Context()->GetDeferredTaskHandler();
+      if (deferred_task_handler.AcceptsTailProcessing())
+        deferred_task_handler.AddTailProcessingHandler(this);
     } else {
       DisableOutputs();
     }

third_party/blink/renderer/modules/webaudio/base_audio_context.cc

@@ -612,6 +612,9 @@ void BaseAudioContext::SetContextState(AudioContextState new_state) {
                              WrapPersistent(this)));
   }
 
+  if (new_state == kClosed)
+    GetDeferredTaskHandler().StopAcceptingTailProcessing();
+
   // Notify context that state changed
   if (GetExecutionContext()) {
     GetExecutionContext()

third_party/blink/renderer/modules/webaudio/deferred_task_handler.cc

@@ -167,6 +167,7 @@ void DeferredTaskHandler::ProcessAutomaticPullNodes(size_t frames_to_process) {
 
 void DeferredTaskHandler::AddTailProcessingHandler(
     scoped_refptr<AudioHandler> handler) {
+  DCHECK(accepts_tail_processing_);
   AssertGraphOwner();
 
   if (!tail_processing_handlers_.Contains(handler)) {

third_party/blink/renderer/modules/webaudio/deferred_task_handler.h

@@ -109,6 +109,9 @@ class MODULES_EXPORT DeferredTaskHandler final
   void RequestToDeleteHandlersOnMainThread();
   void ClearHandlersToBeDeleted();
 
+  bool AcceptsTailProcessing() const { return accepts_tail_processing_; }
+  void StopAcceptingTailProcessing() { accepts_tail_processing_ = false; }
+
   // If |node| requires tail processing, add it to the list of tail
   // nodes so the tail is processed.
   void AddTailProcessingHandler(scoped_refptr<AudioHandler>);
@@ -228,11 +231,16 @@ class MODULES_EXPORT DeferredTaskHandler final
 
   // Nodes that are processing its tail.
   Vector<scoped_refptr<AudioHandler>> tail_processing_handlers_;
+
   // Tail processing nodes that are now finished and want the output to be
   // disabled.  This is updated in the audio thread (with the graph lock).  The
   // main thread will disable the outputs.
   Vector<scoped_refptr<AudioHandler>> finished_tail_processing_handlers_;
 
+  // Once the associated context closes, new tail processing handlers are not
+  // accepted.
+  bool accepts_tail_processing_ = true;
+
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   // Graph locking.