Convert channel counts to size_t.

webrtc/modules/audio_coding/acm2/audio_coding_module.cc

Index: webrtc/modules/audio_coding/acm2/audio_coding_module.cc
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module.cc b/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
index 034de32cb6c0df5fce1a372b634a3afe974c12d6..c4dd349cc4ddb3eeebf992a3456d8e93a647fcb7 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
@@ -56,7 +56,7 @@ int AudioCodingModule::Codec(int list_id, CodecInst* codec) {
 int AudioCodingModule::Codec(const char* payload_name,
                              CodecInst* codec,
                              int sampling_freq_hz,
-                             int channels) {
+                             size_t channels) {
   rtc::Optional<CodecInst> ci = acm2::RentACodec::CodecInstByParams(
       payload_name, sampling_freq_hz, channels);
   if (ci) {
@@ -76,7 +76,7 @@ int AudioCodingModule::Codec(const char* payload_name,
 
 int AudioCodingModule::Codec(const char* payload_name,
                              int sampling_freq_hz,
-                             int channels) {
+                             size_t channels) {
   rtc::Optional<acm2::RentACodec::CodecId> ci =
       acm2::RentACodec::CodecIdByParams(payload_name, sampling_freq_hz,
                                         channels);