Fix Chromium style checker warnings for MockAudioDecoder

webrtc/test/mock_audio_decoder.h

Index: webrtc/test/mock_audio_decoder.h
diff --git a/webrtc/test/mock_audio_decoder.h b/webrtc/test/mock_audio_decoder.h
index 883002112024b7a51ee71810d0e14f696ed44662..d124b0f8a15acba58383df2b33eeb81fd44c0a26 100644
--- a/webrtc/test/mock_audio_decoder.h
+++ b/webrtc/test/mock_audio_decoder.h
@@ -18,8 +18,8 @@ namespace webrtc {
 
 class MockAudioDecoder : public AudioDecoder {
  public:
-  MockAudioDecoder() {}
-  virtual ~MockAudioDecoder() { Die(); }
+  MockAudioDecoder();
+  ~MockAudioDecoder();
   MOCK_METHOD0(Die, void());
   MOCK_METHOD5(DecodeInternal,
                int(const uint8_t*, size_t, int, int16_t*, SpeechType*));