Suppress excessive logging in video_coding

Only prints the warning message if a frame was dropped.

R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/1735004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4278 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed