Oilpan: WebAudio: Prepare to move AudioProcessor hierarchy to Oilpan heap.

Source/platform/audio/AudioProcessor.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 19 matching lines @@
 
 #include "config.h"
 #include "platform/audio/AudioProcessor.h"
 
 namespace blink {
 
 AudioProcessor::~AudioProcessor()
 {
 }
 
+void AudioProcessor::trace(Visitor*)
+{
+}
+
 }