Make screenshare target bitrate experiment always on

BUG=4083
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44699004

Patch from sprang@webrtc.org <sprang@webrtc.org>.

Cr-Commit-Position: refs/heads/master@{#8806}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8806 4adac7df-926f-26a2-2b94-8c16560cd09d
3 files changed