Set thread scheduling parameters inside the new thread.

This makes it possible to restrict threads from modifying scheduling
parameters of another thread in the Chrome Linux sandbox.

BUG=
R=henrike@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/28539004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7324 4adac7df-926f-26a2-2b94-8c16560cd09d