Remove I420VideoFrame::CloneFrame

This function is not needed anymore.

BUG=1128
R=stefan@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42899004

Cr-Commit-Position: refs/heads/master@{#8843}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8843 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed