Replace VideoFrameI420 with I420VideoFrame.

Gives one less struct/class for I420 video frames.

BUG=2657
R=mflodman@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/4149004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5160 4adac7df-926f-26a2-2b94-8c16560cd09d
7 files changed