Clean up VideoRenderFrames

It's possible to clean up VideoRenderFrames now when I420VideoFrame holds a reference counted frame buffer.

BUG=1128
R=mflodman@webrtc.org, pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48459004

Cr-Commit-Position: refs/heads/master@{#8695}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8695 4adac7df-926f-26a2-2b94-8c16560cd09d
3 files changed