Since Chromium has moved to this policy, we should too.
Code is copied from /depot_tools/presubmit_canned_checks.py but modified for our purpose.
BUG=
TEST=Tested git cl presubmit with a modified .cc file with the 2011 header and one with the 2012.
Review URL: https://webrtc-codereview.appspot.com/770005
git-svn-id: http://webrtc.googlecode.com/svn/trunk@2691 4adac7df-926f-26a2-2b94-8c16560cd09d