* Add a RingBuffer typedef.
* Add the ability to force a memcpy by passing a null ptr. In some cases,
we know we want a memcpy. This allows us to skip a potential
intermediate memcpy.
* Add a stress test.
Review URL: https://webrtc-codereview.appspot.com/1111004
git-svn-id: http://webrtc.googlecode.com/svn/trunk@3567 4adac7df-926f-26a2-2b94-8c16560cd09d