Have the mac port support per_test_timeout in webkitpy
https://bugs.webkit.org/show_bug.cgi?id=112466

Reviewed by Dirk Pranke.

Both WTR and DRT handle --timeout arguments, so we can
have the scripts pass the timeout values down to the tools.

* Scripts/webkitpy/layout_tests/port/mac.py:
(MacPort.supports_per_test_timeout):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145948 268f45cc-cd09-0410-ab3c-d52691b4dbfc