Remove the video channel id completely.

BUG=webrtc:5079

Review URL: https://codereview.webrtc.org/1412143002

Cr-Original-Commit-Position: refs/heads/master@{#10324}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0dbf0090a961c5e5fb7362937108337564b4a91f
8 files changed