This affects the webrtc::VideoFrameBuffer and cricket::VideoFrame
classes.
To make this work, VideoFrameFactory is changed to use an
I420BufferPool rather than a plain VideoFrame to cache allocated
frames.
The I420BufferPool is reorganized to return an I420Buffer,
rather than a proxy object.
BUG=webrtc:5921, webrtc:5682
Review-Url: https://codereview.webrtc.org/2009193002
Cr-Commit-Position: refs/heads/master@{#12919}
d591e3fcf3