Update gtk exclusion rules to account for test files.

BUG=None
TEST=webkit_unit_tests
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/47353003

git-svn-id: svn://svn.chromium.org/blink/trunk@160681 bbb929c8-8fbe-4397-9dbb-9b2b20218538