Make rtcp parsing implementation private in RtcpReceiver: Function just for Parse and for Callbacks moved to private section. All handles moved from protected to private section.
Make rtcp parsing implementation private in RtcpReceiver:
Function just for Parse and for Callbacks moved to private section.
All handles moved from protected to private section.

BUG=webrtc:5260
R=sprang@webrtc.org

Review URL: https://codereview.webrtc.org/2320603002 .

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#14181}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: faf708e238c7b43a732fbebf79ac9298b4b95a95

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk