Adds support for finch experiments to video_loopback.

Adds support for logging to stderr via -logs.

Enables abs-send-time by default.

R=mflodman@webrtc.org, pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/23329004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7613 4adac7df-926f-26a2-2b94-8c16560cd09d