Revert "Revert "Remove frame copy from cricket::VideoFrame to I420VideoFrame""

This reverts r8683 and is a reland of r8682.

Reason for revert: The thread checker in Chromium that crashed has been fixed now.

BUG=1128
TBR=tommi,pbos,pthatcher

Review URL: https://webrtc-codereview.appspot.com/40319004

Cr-Commit-Position: refs/heads/master@{#8696}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8696 4adac7df-926f-26a2-2b94-8c16560cd09d
8 files changed