Fix Chromium clang plugin warnings

NOTRY=true
BUG=webrtc:163

Review-Url: https://codereview.webrtc.org/2291503002
Cr-Commit-Position: refs/heads/master@{#13959}
diff --git a/webrtc/modules/audio_coding/test/utility.h b/webrtc/modules/audio_coding/test/utility.h
index 23869be..dbd398e 100644
--- a/webrtc/modules/audio_coding/test/utility.h
+++ b/webrtc/modules/audio_coding/test/utility.h
@@ -118,10 +118,8 @@
 class VADCallback : public ACMVADCallback {
  public:
   VADCallback();
-  ~VADCallback() {
-  }
 
-  int32_t InFrameType(FrameType frame_type);
+  int32_t InFrameType(FrameType frame_type) override;
 
   void PrintFrameTypes();
   void Reset();