Break out RemoteBitrateEstimator from RtpRtcp module and make RemoteBitrateEstimator::Process trigger new REMB messages.

Also make sure RTT is computed independently of whether it's time to send RTCP messages or not.

BUG=1298

Review URL: https://webrtc-codereview.appspot.com/1060005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3455 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/rtp_rtcp/interface/rtp_rtcp.h

@@ -462,12 +462,6 @@ class RtpRtcp : public Module {
                              WebRtc_UWord32* fecRate,
                              WebRtc_UWord32* nackRate) const = 0;
 
-    /*
-     *  Get the receive-side estimate of the available bandwidth.
-     */
-    virtual int EstimatedReceiveBandwidth(
-        WebRtc_UWord32* available_bandwidth) const = 0;
-
     /*
     *   Used by the codec module to deliver a video or audio frame for
     *   packetization.