Reland "Avoid critsect for protection- and qm setting callbacks in
VideoSender."

The original Cl is uploaded as patch set 1, the fix in ps#2 and I'll rebase in ps#3.

BUG=4534
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/46769004

Cr-Commit-Position: refs/heads/master@{#9000}
18 files changed