Consolidate common_video targets to improve gyp run time.

Not sure if this change is measurable; perhaps a 1% savings.

BUG=webrtc:34

Review URL: https://webrtc-codereview.appspot.com/785005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@2732 4adac7df-926f-26a2-2b94-8c16560cd09d
12 files changed