When a frame being stretched, the original rotation information is lost. This is to ensure it's carried over.
Also removed StretchToBuffer function as it's not called and dangerous.
BUG=4366
R=pthatcher@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/51869004
Cr-Commit-Position: refs/heads/master@{#9224}
