Remove webrtc::Config from ViEChannelGroup.

Also removing webrtc/experiments.h which is no longer used.

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

Review URL: https://codereview.webrtc.org/1250513006

Cr-Commit-Position: refs/heads/master@{#9642}
12 files changed