Propagate estimated RTT from receivers to rtt observer.

BUG=1613
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/3119004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5063 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_receiver.h b/webrtc/modules/rtp_rtcp/source/rtcp_receiver.h
index 0b5c8f1..3da3445 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_receiver.h
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_receiver.h
@@ -86,6 +86,8 @@
 
     int32_t SenderInfoReceived(RTCPSenderInfo* senderInfo) const;
 
+    bool GetAndResetXrRrRtt(uint16_t* rtt_ms);
+
     // get statistics
     int32_t StatisticsReceived(
         std::vector<RTCPReportBlock>* receiveBlocks) const;
@@ -245,6 +247,8 @@
   // Time when the report was received.
   uint32_t _lastReceivedXRNTPsecs;
   uint32_t _lastReceivedXRNTPfrac;
+  // Estimated rtt, zero when there is no valid estimate.
+  uint16_t xr_rr_rtt_ms_;
 
   // Received report blocks.
   std::map<uint32_t, RTCPHelp::RTCPReportBlockInformation*>