Revert 8260 "Base RWLockWrapper on rtc::SharedExclusiveLock."
Unfortunately this caused channel teardown to hang.
More details in email(s).

> Base RWLockWrapper on rtc::SharedExclusiveLock.
>
> Also moves rtc::Event and rtc::SharedExclusiveLock to rtc_base_approved.
>
> R=tommi@webrtc.org
> BUG=
>
> Review URL: https://webrtc-codereview.appspot.com/38889004

TBR=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/34999005

Cr-Commit-Position: refs/heads/master@{#8284}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8284 4adac7df-926f-26a2-2b94-8c16560cd09d
14 files changed