Split audio mixer into interface and implementation.

webrtc/modules/audio_mixer/audio_frame_manipulator.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/audio_mixer/audio_frame_manipulator.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/modules/utility/include/audio_frame_operations.h"
-#include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 uint32_t AudioMixerCalculateEnergy(const AudioFrame& audio_frame) {
   uint32_t energy = 0;
   for (size_t position = 0; position < audio_frame.samples_per_channel_;
        position++) {
     // TODO(aleloi): This can overflow. Convert to floats.
     energy += audio_frame.data_[position] * audio_frame.data_[position];
   }
@@ skipping 22 matching lines @@
 void RemixFrame(size_t target_number_of_channels, AudioFrame* frame) {
   RTC_DCHECK_GE(target_number_of_channels, 1u);
   RTC_DCHECK_LE(target_number_of_channels, 2u);
   if (frame->num_channels_ == 1 && target_number_of_channels == 2) {
     AudioFrameOperations::MonoToStereo(frame);
   } else if (frame->num_channels_ == 2 && target_number_of_channels == 1) {
     AudioFrameOperations::StereoToMono(frame);
   }
 }
 }  // namespace webrtc