Optimize NACK list creation.

- No longer looping through all frame buffers.
- Keeping track of the current nack list index when building the list.
- Don't look for changes in the NACK list if the size has increased.

Review URL: https://webrtc-codereview.appspot.com/1076005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3420 4adac7df-926f-26a2-2b94-8c16560cd09d

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

@@ -67,10 +67,11 @@ public:
     // NACK - Building the NACK lists.
     // Build hard NACK list: Zero out all entries in list up to and including
     // _lowSeqNum.
-    int BuildHardNackList(int* list, int num);
+    int BuildHardNackList(int* list, int num, int nack_seq_nums_index);
     // Build soft NACK list: Zero out only a subset of the packets, discard
     // empty packets.
-    int BuildSoftNackList(int* list, int num, int rttMs);
+    int BuildSoftNackList(int* list, int num, int nack_seq_nums_index,
+                          int rttMs);
     void IncrementNackCount();
     WebRtc_Word16 GetNackCount() const;