Fix BaseAudioContext::hasPendingActivity() to make it GCed correctly

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

 /*
  * Copyright (C) 2010, 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 17 matching lines @@
 #include "modules/webaudio/BaseAudioContext.h"
 #include "platform/audio/AudioUtilities.h"
 #include "platform/audio/DenormalDisabler.h"
 #include "wtf/Atomics.h"
 
 namespace blink {
 
 AudioDestinationHandler::AudioDestinationHandler(AudioNode& node, float sampleRate)
     : AudioHandler(NodeTypeDestination, node, sampleRate)
     , m_currentSampleFrame(0)
+    , m_numberOfConnections(0)
 {
     addInput();
 }
 
 AudioDestinationHandler::~AudioDestinationHandler()
 {
     DCHECK(!isInitialized());
 }
 
 void AudioDestinationHandler::render(AudioBus* sourceBus, AudioBus* destinationBus, size_t numberOfFrames)
@@ skipping 48 matching lines @@
 
     // Process nodes which need a little extra help because they are not connected to anything, but still need to process.
     context()->deferredTaskHandler().processAutomaticPullNodes(numberOfFrames);
 
     // Let the context take care of any business at the end of each render quantum.
     context()->handlePostRenderTasks();
 
     // Advance current sample-frame.
     size_t newSampleFrame = m_currentSampleFrame + numberOfFrames;
     releaseStore(&m_currentSampleFrame, newSampleFrame);
+
+    // Update connection status.
+    releaseStore(&m_numberOfConnections, input(0).numberOfRenderingConnections());
+}
+
+unsigned AudioDestinationHandler::numberOfConnections() const
+{
+    return acquireLoad(&m_numberOfConnections);
 }
 
 // ----------------------------------------------------------------
 
 AudioDestinationNode::AudioDestinationNode(BaseAudioContext& context)
     : AudioNode(context)
 {
 }
 
 AudioDestinationHandler& AudioDestinationNode::audioDestinationHandler() const
 {
     return static_cast<AudioDestinationHandler&>(handler());
 }
 
 unsigned long AudioDestinationNode::maxChannelCount() const
 {
     return audioDestinationHandler().maxChannelCount();
 }
 
+bool AudioDestinationNode::hasConnection() const
+{
+    return audioDestinationHandler().numberOfConnections() > 0;
+}

[Raymond Toy, 2016/08/26 20:12:15]

Since AudioDestinationNode is an AudioNode with a single input, can't this all
be done using audioDestinationHandler()->input(0)->isConnected()?  (See
PannerHandler::process for an example).

This gets rid of a lot of redundant stuff, if this actually works.

[hongchan, 2016/08/27 17:09:40]

As we discussed offline, this structure is necessary because the active
connection of the input summing junction can only be touched by the audio
rendering thread. So I am using the atomic access with a proxy variable, but
this causes the renderer crash in WebAudio layout tests.

+
 } // namespace blink