Cleanup test_support target names.

In GN it is redundat to include the parent directory name, as in
ui/gfx:gfx_test_support. Instead we can write it as ui/gfx:test_support
which is shorter and nicer to read.

Targets found with the following command line:
$ for f in $(g ls-files | grep BUILD); do grep _test_support $f; echo
$f; done


Review URL:

git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98
12 files changed