VCM: Adding API for the size(duration) of the jitter buffer.

Refers to the duration in time of the frames which are ready to be sent to the decoder.

Review URL: https://webrtc-codereview.appspot.com/1319004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3903 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/video_coding/main/source/receiver.h

@@ -80,6 +80,10 @@ class VCMReceiver {
   void SetDecodeWithErrors(bool enable);
   bool DecodeWithErrors() const;
 
+  // Returns size in time (milliseconds) of complete continuous frames in the
+  // jitter buffer.
+  int RenderBufferSizeMs();
+
  private:
   VCMEncodedFrame* FrameForDecoding(uint16_t max_wait_time_ms,
                                     int64_t nextrender_time_ms,