Prevent audio thread access to finished, non-active AudioNodes.

third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.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 769 matching lines @@
     }
     m_finishedSourceNodes.clear();
 }
 
 void AbstractAudioContext::releaseFinishedSourceNodes()
 {
     ASSERT(isGraphOwner());
     ASSERT(isAudioThread());
     bool didRemove = false;
     for (AudioHandler* handler : m_finishedSourceHandlers) {
-        for (unsigned i = 0; i < m_activeSourceNodes.size(); ++i) {
-            if (handler == &m_activeSourceNodes[i]->handler()) {
+        for (AudioNode* node : m_activeSourceNodes) {
+            if (m_finishedSourceNodes.contains(node))
+                continue;
+            if (handler == &node->handler()) {
                 handler->breakConnection();
-                m_finishedSourceNodes.append(m_activeSourceNodes[i]);
+                m_finishedSourceNodes.add(node);
                 didRemove = true;
                 break;
             }
         }
     }
     if (didRemove)
         Platform::current()->mainThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, threadSafeBind(&AbstractAudioContext::removeFinishedSourceNodes, this));
 
     m_finishedSourceHandlers.clear();
 }
@@ skipping 15 matching lines @@
 
     m_activeSourceNodes.clear();
 }
 
 void AbstractAudioContext::handleStoppableSourceNodes()
 {
     ASSERT(isGraphOwner());
 
     // Find AudioBufferSourceNodes to see if we can stop playing them.
     for (AudioNode* node : m_activeSourceNodes) {
+        if (m_finishedSourceNodes.contains(node))

[Raymond Toy, 2016/05/10 16:04:20]

Can you add a comment here why you're skipping active nodes that are deemed
finished?

In 6 mo, I will forget why this is here. :-(

[sof, 2016/05/10 19:09:09]

Added comment, let's see if it makes sense in 6 months time :)

[Raymond Toy, 2016/05/10 19:54:57]

Excellent!  At least I'll have some understanding of why, even if I don't fully
remember. :-)

+            continue;
         if (node->handler().getNodeType() == AudioHandler::NodeTypeAudioBufferSource) {
             AudioBufferSourceNode* sourceNode = static_cast<AudioBufferSourceNode*>(node);
             sourceNode->audioBufferSourceHandler().handleStoppableSourceNode();
         }
     }
 }
 
 void AbstractAudioContext::handlePreRenderTasks()
 {
     ASSERT(isAudioThread());
@@ skipping 129 matching lines @@
 
 SecurityOrigin* AbstractAudioContext::getSecurityOrigin() const
 {
     if (getExecutionContext())
         return getExecutionContext()->getSecurityOrigin();
 
     return nullptr;
 }
 
 } // namespace blink
-