Change the static_library("webrtc") to a source set in the GN build.

Static libraries cannot have only headers as sources (libtool complains
that there's nothing to actually link).

TBR=brettw@chromium.org

Review URL: https://webrtc-codereview.appspot.com/27159004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7687 4adac7df-926f-26a2-2b94-8c16560cd09d
VideoSendStreamTest.SwapsI420VideoFrames: Initialize frame memory to avoid drmemory errors

R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/27149004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7688 4adac7df-926f-26a2-2b94-8c16560cd09d
webrtc::Scaler: Preserve aspect ratio

BUG=3936
R=glaznev@webrtc.org, stefan@webrtc.org

Committed: https://code.google.com/p/webrtc/source/detail?r=7679

Review URL: https://webrtc-codereview.appspot.com/28969004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7689 4adac7df-926f-26a2-2b94-8c16560cd09d