AudioBufferSourceNode.buffer can only be set once.

Source/modules/webaudio/AudioBufferSourceNode.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 13 matching lines @@
 
 #include "config.h"
 
 #if ENABLE(WEB_AUDIO)
 
 #include "modules/webaudio/AudioBufferSourceNode.h"
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/frame/UseCounter.h"
 #include "platform/audio/AudioUtilities.h"
 #include "modules/webaudio/AudioContext.h"
 #include "modules/webaudio/AudioNodeOutput.h"
 #include "platform/FloatConversion.h"
 #include "wtf/MainThread.h"
 #include "wtf/MathExtras.h"
 #include <algorithm>
 
 namespace blink {
 
@@ skipping 290 matching lines @@
     m_virtualReadIndex = virtualReadIndex;
 
     return true;
 }
 
 
 void AudioBufferSourceNode::setBuffer(AudioBuffer* buffer, ExceptionState& exceptionState)
 {
     ASSERT(isMainThread());
 
+    if (m_buffer) {
+        // Setting the buffer more than once is deprecated.  Change this to a DOM exception in M45
+        // or so.
+        UseCounter::countDeprecation(context()->executionContext(), UseCounter::AudioBufferSourceBufferOnce);
+    }
+
     // The context must be locked since changing the buffer can re-configure the number of channels that are output.
     AudioContext::AutoLocker contextLocker(context());
 
     // This synchronizes with process().
     MutexLocker processLocker(m_processLock);
 
     if (buffer) {
         // Do any necesssary re-configuration to the buffer's number of channels.
         unsigned numberOfChannels = buffer->numberOfChannels();
 
@@ skipping 171 matching lines @@
 {
     visitor->trace(m_buffer);
     visitor->trace(m_playbackRate);
     visitor->trace(m_pannerNode);
     AudioScheduledSourceNode::trace(visitor);
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)