Revert of Lock out GCs while iterating over MediaStreamSource audio consumers.

third_party/WebKit/Source/platform/mediastream/MediaStreamSource.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
@@ skipping 89 matching lines @@
                                        float sampleRate) {
   ASSERT(m_requiresConsumer);
   MutexLocker locker(m_audioConsumersLock);
   for (AudioDestinationConsumer* consumer : m_audioConsumers)
     consumer->setFormat(numberOfChannels, sampleRate);
 }
 
 void MediaStreamSource::consumeAudio(AudioBus* bus, size_t numberOfFrames) {
   ASSERT(m_requiresConsumer);
   MutexLocker locker(m_audioConsumersLock);
-  // Prevent GCs from going ahead while this iteration runs, attempting to
-  // pinpoint crbug.com/682945 failures.
-  ThreadState::MainThreadGCForbiddenScope scope;
   for (AudioDestinationConsumer* consumer : m_audioConsumers)
     consumer->consumeAudio(bus, numberOfFrames);
 }
 
 DEFINE_TRACE(MediaStreamSource) {
   visitor->trace(m_observers);
 }
 
 }  // namespace blink