GitLab

This is pretty straightforward, just moving the screen_unittest.cc
entries from ui_unittests.gyp to gfx_tests.gyp. gfx_unittests now has a
TestSuite that setups everything we need to run it.

BUG=331829
TEST=ui_unittests, gfx_unittests
TBR=ben@chromium.org,danakj@chromium.org

Review URL: https://codereview.chromium.org/384263002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284458 0039d316-1c4b-4281-b951-d872f2087c98