Revert 7679 "webrtc::Scaler: Preserve aspect ratio"

> webrtc::Scaler: Preserve aspect ratio
> 
> BUG=3936
> R=glaznev@webrtc.org, stefan@webrtc.org
> 
> Review URL: https://webrtc-codereview.appspot.com/28969004

TBR=magjed@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/30989004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7682 4adac7df-926f-26a2-2b94-8c16560cd09d