Use a manual reset event in PosixThread.
This fixes occasional hangs we've been seeing in the past few days. I'm using rtc::Event instead of the EventWrapper, so I'll wait with landing this cl until I've made that change in a separate cl.

BUG=2822,4282
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/38009004

Cr-Commit-Position: refs/heads/master@{#8293}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8293 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed