Convert channel counts to size_t.

webrtc/modules/audio_processing/common.h

 /*
  *  Copyright (c) 2014 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_PROCESSING_COMMON_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_COMMON_H_
 
 #include <assert.h>
 
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 
 namespace webrtc {
 
-static inline int ChannelsFromLayout(AudioProcessing::ChannelLayout layout) {
+static inline size_t ChannelsFromLayout(AudioProcessing::ChannelLayout layout) {
   switch (layout) {
     case AudioProcessing::kMono:
     case AudioProcessing::kMonoAndKeyboard:
       return 1;
     case AudioProcessing::kStereo:
     case AudioProcessing::kStereoAndKeyboard:
       return 2;
   }
   assert(false);
   return 0;
 }
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_COMMON_H_