[NOT FOR REVIEW] Convert channel counts to size_t.

webrtc/modules/audio_processing/level_estimator_impl.cc

Index: webrtc/modules/audio_processing/level_estimator_impl.cc
diff --git a/webrtc/modules/audio_processing/level_estimator_impl.cc b/webrtc/modules/audio_processing/level_estimator_impl.cc
index 26a61dcdb566b14ac807bdbc4cf613763bd48918..91308b956ac5f4da754cd9d249b7bae4bb35b79a 100644
--- a/webrtc/modules/audio_processing/level_estimator_impl.cc
+++ b/webrtc/modules/audio_processing/level_estimator_impl.cc
@@ -30,7 +30,7 @@ int LevelEstimatorImpl::ProcessStream(AudioBuffer* audio) {
   }
 
   RMSLevel* rms_level = static_cast<RMSLevel*>(handle(0));
-  for (int i = 0; i < audio->num_channels(); ++i) {
+  for (size_t i = 0; i < audio->num_channels(); ++i) {
     rms_level->Process(audio->channels_const()[i],
                        audio->num_frames());
   }
@@ -75,7 +75,7 @@ int LevelEstimatorImpl::ConfigureHandle(void* /*handle*/) const {
   return AudioProcessing::kNoError;
 }
 
-int LevelEstimatorImpl::num_handles_required() const {
+size_t LevelEstimatorImpl::num_handles_required() const {
   return 1;
 }