Update audio code to use size_t more correctly, webrtc/common_audio/ portion.

webrtc/common_audio/vad/vad_core_unittest.cc

Index: webrtc/common_audio/vad/vad_core_unittest.cc
diff --git a/webrtc/common_audio/vad/vad_core_unittest.cc b/webrtc/common_audio/vad/vad_core_unittest.cc
index 77db3d8ed23fdc450fe0a18010d496330c5644e7..ee69484f0a1dbf40090ba6d125a20f71346751f7 100644
--- a/webrtc/common_audio/vad/vad_core_unittest.cc
+++ b/webrtc/common_audio/vad/vad_core_unittest.cc
@@ -82,8 +82,8 @@ TEST_F(VadTest, CalcVad) {
 
   // Construct a speech signal that will trigger the VAD in all modes. It is
   // known that (i * i) will wrap around, but that doesn't matter in this case.
-  for (int16_t i = 0; i < kMaxFrameLength; ++i) {
-    speech[i] = (i * i);
+  for (size_t i = 0; i < kMaxFrameLength; ++i) {
+    speech[i] = static_cast<int16_t>(i * i);
   }
   for (size_t j = 0; j < kFrameLengthsSize; ++j) {
     if (ValidRatesAndFrameLengths(8000, kFrameLengths[j])) {