libyuv

Change to using gyp_chromium for gtest dependencies.

Pulling in gtest for unit testing also pulls in
chromium build parts.  Using the model that WebRTC does
for including gtest.
Review URL: http://webrtc-codereview.appspot.com/190007

git-svn-id: http://libyuv.googlecode.com/svn/trunk@10 16f28f9a-4ce2-e073-06de-1de4eb20be90