Fix regression with audio mirroring due to observers being added while iterating over the list of ob

media/audio/audio_manager_base.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/audio_manager_base.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/thread.h"
@@ skipping 29 matching lines @@
 
 const char AudioManagerBase::kDefaultDeviceName[] = "Default";
 const char AudioManagerBase::kDefaultDeviceId[] = "default";
 
 AudioManagerBase::AudioManagerBase()
     : num_active_input_streams_(0),
       max_num_output_streams_(kDefaultMaxOutputStreams),
       max_num_input_streams_(kDefaultMaxInputStreams),
       num_output_streams_(0),
       num_input_streams_(0),
+      output_listeners_(
+          ObserverList<AudioDeviceListener>::NOTIFY_EXISTING_ONLY),
       audio_thread_(new base::Thread("AudioThread")),
       virtual_audio_input_stream_(NULL) {
 #if defined(OS_WIN)
   audio_thread_->init_com_with_mta(true);
 #endif
   CHECK(audio_thread_->Start());
   message_loop_ = audio_thread_->message_loop_proxy();
 }
 
 AudioManagerBase::~AudioManagerBase() {
@@ skipping 334 matching lines @@
   output_listeners_.RemoveObserver(listener);
 }
 
 void AudioManagerBase::NotifyAllOutputDeviceChangeListeners() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   DVLOG(1) << "Firing OnDeviceChange() notifications.";
   FOR_EACH_OBSERVER(AudioDeviceListener, output_listeners_, OnDeviceChange());
 }
 
 }  // namespace media