Keep AudioSourceNode from premature GC with ScriptWrappable::hasPendingActivity()

third_party/WebKit/Source/modules/webaudio/AudioScheduledSourceNode.cpp

 /*
  * Copyright (C) 2012, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 207 matching lines @@
 {
     ASSERT(isMainThread());
     if (node())
         node()->dispatchEvent(Event::create(EventTypeNames::ended));
 }
 
 // ----------------------------------------------------------------
 
 AudioScheduledSourceNode::AudioScheduledSourceNode(AbstractAudioContext& context)
     : AudioSourceNode(context)
+    , m_isMarkedForGC(false)
 {
 }
 
 AudioScheduledSourceHandler& AudioScheduledSourceNode::audioScheduledSourceHandler() const
 {
     return static_cast<AudioScheduledSourceHandler&>(handler());
 }
 
-void AudioScheduledSourceNode::start(ExceptionState& exceptionState)
+void AudioScheduledSourceNode::startNode(ExceptionState& exceptionState)
 {
-    start(0, exceptionState);
+    startNode(0, exceptionState);
 }
 
-void AudioScheduledSourceNode::start(double when, ExceptionState& exceptionState)
+void AudioScheduledSourceNode::startNode(double when, ExceptionState& exceptionState)
 {
     audioScheduledSourceHandler().start(when, exceptionState);
 }
 
-void AudioScheduledSourceNode::stop(ExceptionState& exceptionState)
+void AudioScheduledSourceNode::stopNode(ExceptionState& exceptionState)
 {
-    stop(0, exceptionState);
+    stopNode(0, exceptionState);
 }
 
-void AudioScheduledSourceNode::stop(double when, ExceptionState& exceptionState)
+void AudioScheduledSourceNode::stopNode(double when, ExceptionState& exceptionState)
 {
     audioScheduledSourceHandler().stop(when, exceptionState);
 }
 
 EventListener* AudioScheduledSourceNode::onended()
 {
     return getAttributeEventListener(EventTypeNames::ended);
 }
 
 void AudioScheduledSourceNode::setOnended(PassRefPtrWillBeRawPtr<EventListener> listener)
 {
     setAttributeEventListener(EventTypeNames::ended, listener);
 }
 
+void AudioScheduledSourceNode::markForGC()
+{
+    m_isMarkedForGC = true;
+}
+
+bool AudioScheduledSourceNode::hasPendingActivity() const
+{
+    // AudioScheduledSourceNodes (i.e. Oscillator and BufferSource) are marked
+    // as following:
+    // - if released from the context: do GC.
+    // - when playing or scheduled: has pending activity, do not GC.
+    // - when unscheduled or finished: no pending activity, do GC.
+    if (m_isMarkedForGC)

[haraken, 2016/02/19 17:46:00]

Instead of introducing m_isMarkedForGC, can we do something like:

  if (context()->isStopped())
    return;

?

Then you don't need to propagate markedForGC to all AudioNodes. Also it is
common to check the status of ExecutionContext (or its friends) in
hasPendingActivity.

[hongchan, 2016/02/19 18:13:48]

Good idea. Done.

+        return false;
+
+    return audioScheduledSourceHandler().isPlayingOrScheduled();
+}
+
 } // namespace blink