Unify newapi::RtcpMode and RTCPMethod.
Unify newapi::RtcpMode and RTCPMethod.

BUG=webrtc:1695
R=solenberg@webrtc.org, stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1373903003

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#10143}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: da903eaabbb6c6830efcafc3c2ade1d36f511e43

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