Fix chromium warnings for SdpVideoFormat.

Bug: webrtc:163
Change-Id: I29ad3c00116692f047456df7721ba636bbb2ca89
Reviewed-on: https://webrtc-review.googlesource.com/64723
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22618}

modules/video_coding/codec_timer.h

@@ -22,6 +22,7 @@ namespace webrtc {
 class VCMCodecTimer {
  public:
   VCMCodecTimer();
+  ~VCMCodecTimer();
 
   // Add a new decode time to the filter.
   void AddTiming(int64_t new_decode_time_ms, int64_t now_ms);