add a script to print what type of layout test each arg is (print-layout-test-types)

This is useful for quickly identifying which tests are pixel tests, ref tests, etc.

R=ojan@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/23672051

git-svn-id: svn://svn.chromium.org/blink/trunk@158209 bbb929c8-8fbe-4397-9dbb-9b2b20218538