Add UMA stats for silence AudioInputController.

media/audio/audio_input_controller.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.
 
 #ifndef MEDIA_AUDIO_AUDIO_INPUT_CONTROLLER_H_
 #define MEDIA_AUDIO_AUDIO_INPUT_CONTROLLER_H_
 
 #include <string>
 #include "base/atomicops.h"
 #include "base/callback.h"
@@ skipping 309 matching lines @@
 
   UserInputMonitor* user_input_monitor_;
 
 #if defined(AUDIO_POWER_MONITORING)
   // Scans audio samples from OnData() as input to compute audio levels.
   scoped_ptr<AudioPowerMonitor> audio_level_;
 
   // We need these to be able to feed data to the AudioPowerMonitor.
   media::AudioParameters audio_params_;
   base::TimeTicks last_audio_level_log_time_;
+
+  bool last_audio_level_was_silence_;
+  int silence_counter_;
 #endif
 
   size_t prev_key_down_count_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioInputController);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_INPUT_CONTROLLER_H_