enable chromium_code=1 to increase warning level.  this will enable the same warnings as when built within chrome, helping avoid breakage in future.
BUG=432
TESTED=local windows build
R=bcornell@google.com

Review URL: https://webrtc-codereview.appspot.com/49839004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1386 16f28f9a-4ce2-e073-06de-1de4eb20be90