Use NtpTime in RtcpReceiver instead of pair of uints

BUG=webrtc:5565

Review-Url: https://codereview.webrtc.org/2389703007
Cr-Original-Commit-Position: refs/heads/master@{#14557}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0b4b72797e586730382081d0975649d698c60ac6
2 files changed