CalculateFrequency() results in zero frequency (floating point) if the RTP timestamps in the RTCP list are equal. Added check in UpdateRtcpList to not insert RTCP SR with the same RTP timestamp. BUG=webrtc:5780 Review URL: https://codereview.webrtc.org/1891703002 Cr-Commit-Position: refs/heads/master@{#12429}