Refactor NACK list creation to build the NACK list as packets arrive.

Also fixes a timer bug related to NACKing in the RTP module which could cause packets to only be NACKed twice if there's frequent packet losses.

Note that I decided to remove any selective NACKing for now as I don't think the gain of doing it is big enough compared to the added complexity. The same reasoning for empty packets. None of them will be retransmitted by a smart sender since the sender would know that they aren't needed.

BUG=1420
TEST=video_coding_unittests, vie_auto_test, video_coding_integrationtests, trybots

Review URL: https://webrtc-codereview.appspot.com/1115006

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3599 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/video_coding/main/source/media_optimization.cc

@@ -16,6 +16,7 @@
 #include "webrtc/system_wrappers/interface/clock.h"
 
 namespace webrtc {
+namespace media_optimization {
 
 VCMMediaOptimization::VCMMediaOptimization(WebRtc_Word32 id,
                                            Clock* clock):
@@ -671,4 +672,5 @@ VCMMediaOptimization::InputFrameRate()
     return WebRtc_UWord32 (_incomingFrameRate + 0.5f);
 }
 
-}
+}  // namespace media_optimization
+}  // namespace webrtc