Delete EncodedFrameObserver::OnEncodeTiming.

This callback was used only by the PrintSamplesToFile feature of
video_quality_test, which looks like it has been broken for some time
(due to mixup of capture time and ntp time).

Bug: webrtc:8504
Change-Id: I7d2b55405caeffda582ae0d6fb0e7dfdfce4c5a9
Reviewed-on: https://webrtc-review.googlesource.com/31420
Commit-Queue: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21211}

common_video/include/frame_callback.h

@@ -49,7 +49,6 @@ struct EncodedFrame {
 class EncodedFrameObserver {
  public:
   virtual void EncodedFrameCallback(const EncodedFrame& encoded_frame) = 0;
-  virtual void OnEncodeTiming(int64_t capture_ntp_ms, int encode_duration_ms) {}
 
  protected:
   virtual ~EncodedFrameObserver() {}