Revert of Reset NACK/ACK list when parsing a new RTCP packet. The NACK/ACK frames/packets list need to be res…

Revert of Reset NACK/ACK list when parsing a new RTCP packet. The NACK/ACK frames/packets list need to be res… (patchset #1 id:1 of https://codereview.chromium.org/1875433002/ )

Reason for revert:
This change needs to be slightly modified since M50 does not have the |received_later_frames| set.

Original issue's description:
> Reset NACK/ACK list when parsing a new RTCP packet. The NACK/ACK frames/packets list need to be reset before parsing each RTCP packet as the parser is shared by all RTCP packets on sender side. This caused the performance regression and potentially video freezing as well.
> 
> BUG=600527
> 
> Review URL: https://codereview.chromium.org/1853253003
> 
> Cr-Commit-Position: refs/heads/master@{#385046}
> (cherry picked from commit 411ea14c10f64b67a25985619583a5331e724d57)
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/e877754f597c1c2fa8ff411be0c2c6ade0cd6c9f

TBR=xjz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=600527

[miu, 2016-04-07 20:42:30]

Created Revert of Reset NACK/ACK list when parsing a new RTCP packet. The
NACK/ACK frames/packets list need to be res…

[miu, 2016-04-07 20:42:40]

The CQ bit was checked by miu@chromium.org