Move the REMB summation into RemoteBitrateEstimatorSingleStream.

BUG=

Review URL: https://webrtc-codereview.appspot.com/891004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/src@2946 4adac7df-926f-26a2-2b94-8c16560cd09d
9 files changed