Convert channel counts to size_t.

webrtc/modules/audio_coding/include/audio_coding_module.h

Index: webrtc/modules/audio_coding/include/audio_coding_module.h
diff --git a/webrtc/modules/audio_coding/include/audio_coding_module.h b/webrtc/modules/audio_coding/include/audio_coding_module.h
index 52fe383a885859469a81b707f2d5af066bab038c..9e7991f22f37930ea613c59ea702a9eb22210eba 100644
--- a/webrtc/modules/audio_coding/include/audio_coding_module.h
+++ b/webrtc/modules/audio_coding/include/audio_coding_module.h
@@ -134,7 +134,7 @@ class AudioCodingModule {
   //    0 if succeeded.
   //
   static int Codec(const char* payload_name, CodecInst* codec,
-                   int sampling_freq_hz, int channels);
+                   int sampling_freq_hz, size_t channels);
 
   ///////////////////////////////////////////////////////////////////////////
   // int32_t Codec()
@@ -153,7 +153,7 @@ class AudioCodingModule {
   //   -1 if the codec is not found.
   //
   static int Codec(const char* payload_name, int sampling_freq_hz,
-                   int channels);
+                   size_t channels);
 
   ///////////////////////////////////////////////////////////////////////////
   // bool IsCodecValid()