[NOT FOR REVIEW] Convert channel counts to size_t.

webrtc/modules/audio_processing/common.h

Index: webrtc/modules/audio_processing/common.h
diff --git a/webrtc/modules/audio_processing/common.h b/webrtc/modules/audio_processing/common.h
index ed8a0544c3f26e36bd504b00c74aa37612962063..d4ddb92b509907a42dab74bfa0723a16c6a1ec6e 100644
--- a/webrtc/modules/audio_processing/common.h
+++ b/webrtc/modules/audio_processing/common.h
@@ -17,7 +17,7 @@
 
 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:
@@ -27,7 +27,7 @@ static inline int ChannelsFromLayout(AudioProcessing::ChannelLayout layout) {
       return 2;
   }
   assert(false);
-  return -1;
+  return 0;
 }
 
 }  // namespace webrtc