[Cast] RTT clean-up to the max!

media/cast/sender/frame_sender.cc

Index: media/cast/sender/frame_sender.cc
diff --git a/media/cast/sender/frame_sender.cc b/media/cast/sender/frame_sender.cc
index f338dd9b2b065ce91a7ea98332711478916ff16f..a2d4abd85b0315ae1d32a15ceaeb756f88e57000 100644
--- a/media/cast/sender/frame_sender.cc
+++ b/media/cast/sender/frame_sender.cc
@@ -20,7 +20,6 @@ FrameSender::FrameSender(scoped_refptr<CastEnvironment> cast_environment,
     : cast_environment_(cast_environment),
       transport_sender_(transport_sender),
       ssrc_(ssrc),
-      rtt_available_(false),
       rtcp_interval_(rtcp_interval),
       max_frame_rate_(max_frame_rate),
       num_aggressive_rtcp_reports_sent_(0),
@@ -78,15 +77,9 @@ void FrameSender::SendRtcpReport(bool schedule_future_reports) {
     ScheduleNextRtcpReport();
 }
 
-void FrameSender::OnReceivedRtt(base::TimeDelta rtt,
-                                base::TimeDelta avg_rtt,
-                                base::TimeDelta min_rtt,
-                                base::TimeDelta max_rtt) {
-  rtt_available_ = true;
-  rtt_ = rtt;
-  avg_rtt_ = avg_rtt;
-  min_rtt_ = min_rtt;
-  max_rtt_ = max_rtt;
+void FrameSender::OnMeasuredRoundTripTime(base::TimeDelta rtt) {
+  DCHECK(rtt > base::TimeDelta());
+  current_round_trip_time_ = rtt;
 }
 
 void FrameSender::SetTargetPlayoutDelay(