GitLab

In the CL: 1) VideoSenderConfig and AudioSenderConfig are merged to
FrameSenderConfig. 2) CastRtpParams is removed . RtpParams is directly
converted to/from FrameSenderConfig.

BUG=530839

Review-Url: https://codereview.chromium.org/2113783002
Cr-Commit-Position: refs/heads/master@{#404520}