Convert channel counts to size_t.

webrtc/common_audio/channel_buffer.cc

Index: webrtc/common_audio/channel_buffer.cc
diff --git a/webrtc/common_audio/channel_buffer.cc b/webrtc/common_audio/channel_buffer.cc
index d3dc7c04f773af73aba9849f3df75ff0dead7701..44520c6100bc8e222d89b37db929942b51a723bd 100644
--- a/webrtc/common_audio/channel_buffer.cc
+++ b/webrtc/common_audio/channel_buffer.cc
@@ -13,7 +13,7 @@
 namespace webrtc {
 
 IFChannelBuffer::IFChannelBuffer(size_t num_frames,
-                                 int num_channels,
+                                 size_t num_channels,
                                  size_t num_bands)
     : ivalid_(true),
       ibuf_(num_frames, num_channels, num_bands),
@@ -47,7 +47,7 @@ void IFChannelBuffer::RefreshF() const {
     assert(ivalid_);
     const int16_t* const* int_channels = ibuf_.channels();
     float* const* float_channels = fbuf_.channels();
-    for (int i = 0; i < ibuf_.num_channels(); ++i) {
+    for (size_t i = 0; i < ibuf_.num_channels(); ++i) {
       for (size_t j = 0; j < ibuf_.num_frames(); ++j) {
         float_channels[i][j] = int_channels[i][j];
       }
@@ -61,7 +61,7 @@ void IFChannelBuffer::RefreshI() const {
     assert(fvalid_);
     int16_t* const* int_channels = ibuf_.channels();
     const float* const* float_channels = fbuf_.channels();
-    for (int i = 0; i < ibuf_.num_channels(); ++i) {
+    for (size_t i = 0; i < ibuf_.num_channels(); ++i) {
       FloatS16ToS16(float_channels[i],
                     ibuf_.num_frames(),
                     int_channels[i]);