Remove I420VideoFrame::SwapFrame

The few remaining uses of this function are replaced with I420VideoFrame assignment, similar to scoped_refptr assignment.

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

Review URL: https://webrtc-codereview.appspot.com/42889004

Cr-Commit-Position: refs/heads/master@{#8844}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8844 4adac7df-926f-26a2-2b94-8c16560cd09d
6 files changed