Create a separate thread for pacing.

This CL moves the pacer out from the regular module process thread to
instead use one thread per pacer. This is to get better accuracy for the
paced packets and to avoid overusing the module process thread.

BUG=
TEST=existing tests
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41839004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@8308 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed