Refactor MediaOptimization protection methods.

Makes MediaOptimization::EnableProtectionMethod significantly less
confusing. Also removing some dead methods in VideoSender.

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

Review URL: https://webrtc-codereview.appspot.com/42339004

Cr-Commit-Position: refs/heads/master@{#8693}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8693 4adac7df-926f-26a2-2b94-8c16560cd09d
9 files changed