REGRESSION(r121497): It switched off and broke many unittests

REGRESSION(r121497): It switched off and broke many unittests
https://bugs.webkit.org/show_bug.cgi?id=90371

Patch by Csaba Osztrogonác <ossy@webkit.org> on 2012-07-02
Reviewed by Adam Barth.

* Scripts/webkitpy/layout_tests/port/chromium_mac_unittest.py:
(ChromiumMacPortTest): Use snowleopard as os_version instead of leopard, because it isn't supported anymore.
* Scripts/webkitpy/layout_tests/port/chromium_port_testcase.py:
(ChromiumPortTestCase.test_all_test_configurations): Remove leopard testcases, because it isn't supported anymore.
* Scripts/webkitpy/layout_tests/port/port_testcase.py:
(PortTestCase): Inherit class PortTestCase from unittest.TestCase instead of object.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121701 268f45cc-cd09-0410-ab3c-d52691b4dbfc