Delete unsupported method VideoCodingModule::RegisterDecoderTimingCallback.

The implementation behind this method has been a noop for a long time.

BUG=none

Review-Url: https://codereview.webrtc.org/2757843002
Cr-Commit-Position: refs/heads/master@{#17286}

webrtc/modules/video_coding/include/video_coding_defines.h

@@ -104,21 +104,6 @@ class VCMReceiveStatisticsCallback {
   virtual ~VCMReceiveStatisticsCallback() {}
 };
 
-// Callback class used for informing the user of decode timing info.
-class VCMDecoderTimingCallback {
- public:
-  virtual void OnDecoderTiming(int decode_ms,
-                               int max_decode_ms,
-                               int current_delay_ms,
-                               int target_delay_ms,
-                               int jitter_buffer_ms,
-                               int min_playout_delay_ms,
-                               int render_delay_ms) = 0;
-
- protected:
-  virtual ~VCMDecoderTimingCallback() {}
-};
-
 // Callback class used for telling the user about how to configure the FEC,
 // and the rates sent the last second is returned to the VCM.
 class VCMProtectionCallback {