Fixes two bugs related to padding in the jitter buffer.

- Pad packets (empty) were often NACKed even though they were received.
- Padding only frames (empty) didn't properly update the decoding state,
  and would therefore be NACKed even though they were received.

TEST=trybots

BUG=1150

Review URL: https://webrtc-codereview.appspot.com/966026

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3181 4adac7df-926f-26a2-2b94-8c16560cd09d

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

@@ -115,6 +115,14 @@ class VCMSessionInfo {
   // would be sent to the decoder.
   void UpdateDecodableSession(int rtt_ms);
 
+  // Clears the sequence numbers in |seq_num_list| of any empty packets received
+  // in this session. |index| is an index in the list at which we start looking
+  // for the sequence numbers. When done this function returns the index of the
+  // next element in the list.
+  int ClearOutEmptyPacketSequenceNumbers(int* seq_num_list,
+                                         int seq_num_list_length,
+                                         int index) const;
+
   // If this session has been NACKed by the jitter buffer.
   bool session_nack_;
   bool complete_;