Don't try to print an empty rect in tests

BUG=247614
R=abarth@chromium.org

Review URL: https://chromiumcodereview.appspot.com/20732006

git-svn-id: svn://svn.chromium.org/blink/trunk@155363 bbb929c8-8fbe-4397-9dbb-9b2b20218538