Adds the UserInputMonitor implementation for Mac.

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 269 matching lines @@
 
   // SyncWriter is used only in low-latency mode for synchronous writing.
   SyncWriter* sync_writer_;
 
   static Factory* factory_;
 
   double max_volume_;
 
   UserInputMonitor* user_input_monitor_;
 
+  uint32_t prev_key_down_count_;
+
   // True if any key has been pressed after the last OnData call.
   bool key_pressed_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioInputController);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_INPUT_CONTROLLER_H_