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/decoding_state.h

@@ -31,6 +31,7 @@ class VCMDecodingState {
   // possible, i.e. temporal info, picture ID or sequence number.
   bool ContinuousFrame(const VCMFrameBuffer* frame) const;
   void SetState(const VCMFrameBuffer* frame);
+  void CopyFrom(const VCMDecodingState& state);
   // Set the decoding state one frame back.
   void SetStateOneBack(const VCMFrameBuffer* frame);
   void UpdateEmptyFrame(const VCMFrameBuffer* frame);