Fix wrong timing when audio is muted.

media/audio/audio_output_mixer.h

 // 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.
 
 // AudioOutputMixer is a class that implements browser-side audio mixer.
 // AudioOutputMixer implements both AudioOutputDispatcher and
 // AudioSourceCallback interfaces.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_
@@ skipping 59 matching lines @@
     int pending_bytes;
   };
   typedef std::map<AudioOutputProxy*, ProxyData> ProxyMap;
   ProxyMap proxies_;
 
   // Physical stream for this mixer.
   scoped_ptr<AudioOutputStream> physical_stream_;
 
   // Temporary buffer used when mixing. Allocated in the constructor
   // to avoid constant allocation/deallocation in the callback.
+  // Low-level multimedia code may work better when data is aligned, as it can
+  // use SSEx/AVX intrinsics. We don't want to use platform-specific aligned
+  // memory allocator, it does not work well with scoped_ptr. Just allocate
+  // slightly more and use raw pointer to the aligned data.
   scoped_array<uint8> mixer_data_;
+  uint8* aligned_mixer_data_;
 
   // Used to post delayed tasks to ourselves that we cancel inside Shutdown().
   base::WeakPtrFactory<AudioOutputMixer> weak_this_;
   base::DelayTimer<AudioOutputMixer> close_timer_;
 
   // Size of data in all in-flight buffers.
   int pending_bytes_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputMixer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_