[NOT FOR REVIEW] Convert channel counts to size_t.

webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc

Index: webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
diff --git a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
index 37ce8733fed21268db49a942eb3cb1c7a7a1b76b..e786cc12ec8407e6ccb7f441ae608c665c317e4d 100644
--- a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
+++ b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
@@ -67,8 +67,8 @@ AudioEncoderOpus::AudioEncoderOpus(const Config& config)
       payload_type_(config.payload_type),
       application_(config.application),
       dtx_enabled_(config.dtx_enabled),
-      samples_per_10ms_frame_(static_cast<size_t>(
-          rtc::CheckedDivExact(kSampleRateHz, 100) * num_channels_)),
+      samples_per_10ms_frame_(
+          rtc::CheckedDivExact(kSampleRateHz, 100) * num_channels_),
       packet_loss_rate_(0.0) {
   CHECK(config.IsOk());
   input_buffer_.reserve(num_10ms_frames_per_packet_ * samples_per_10ms_frame_);
@@ -97,7 +97,7 @@ int AudioEncoderOpus::SampleRateHz() const {
   return kSampleRateHz;
 }
 
-int AudioEncoderOpus::NumChannels() const {
+size_t AudioEncoderOpus::NumChannels() const {
   return num_channels_;
 }
 
@@ -193,8 +193,7 @@ AudioEncoder::EncodedInfo AudioEncoderOpus::EncodeInternal(
            num_10ms_frames_per_packet_ * samples_per_10ms_frame_);
   int status = WebRtcOpus_Encode(
       inst_, &input_buffer_[0],
-      rtc::CheckedDivExact(input_buffer_.size(),
-                           static_cast<size_t>(num_channels_)),
+      rtc::CheckedDivExact(input_buffer_.size(), num_channels_),
       max_encoded_bytes, encoded);
   CHECK_GE(status, 0);  // Fails only if fed invalid data.
   input_buffer_.clear();