Simplify AlsaPcmOutputStream and AudioManagerLinux. Code was thread-safe, but now

media/audio/linux/audio_manager_linux.h

 // Copyright (c) 2011 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.
 
 #ifndef MEDIA_AUDIO_LINUX_AUDIO_MANAGER_LINUX_H_
 #define MEDIA_AUDIO_LINUX_AUDIO_MANAGER_LINUX_H_
 
-#include <map>
+#include <set>
 
 #include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
 #include "media/audio/audio_manager_base.h"
 
 class AlsaPcmOutputStream;
 class AlsaWrapper;
 
 class AudioManagerLinux : public AudioManagerBase {
  public:
   AudioManagerLinux();
 
@@ skipping 16 matching lines @@
 
  protected:
   virtual ~AudioManagerLinux();
 
  private:
   // Helper method to query if there is any valid input device
   bool HasAnyValidAudioInputDevice(void** hint);
 
   scoped_ptr<AlsaWrapper> wrapper_;
 
-  base::Lock lock_;
-  std::map<AlsaPcmOutputStream*, scoped_refptr<AlsaPcmOutputStream> >
-      active_streams_;
+  std::set<AlsaPcmOutputStream*> active_streams_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioManagerLinux);
 };
 
 #endif  // MEDIA_AUDIO_LINUX_AUDIO_MANAGER_LINUX_H_