Split audio mixer into interface and implementation.

webrtc/modules/audio_mixer/audio_frame_manipulator.h

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_MIXER_AUDIO_FRAME_MANIPULATOR_H_
 #define WEBRTC_MODULES_AUDIO_MIXER_AUDIO_FRAME_MANIPULATOR_H_
 
 #include "webrtc/modules/include/module_common_types.h"
-#include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 // Updates the audioFrame's energy (based on its samples).
 uint32_t AudioMixerCalculateEnergy(const AudioFrame& audio_frame);
 
 // Ramps up or down the provided audio frame. Ramp(0, 1, frame) will
 // linearly increase the samples in the frame from 0 to full volume.
 void Ramp(float start_gain, float target_gain, AudioFrame* audio_frame);
 
 // Downmixes or upmixes a frame between stereo and mono.
 void RemixFrame(size_t target_number_of_channels, AudioFrame* frame);
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_MIXER_AUDIO_FRAME_MANIPULATOR_H_