OS X - always use "classic theme" when running Layout tests
OS X - always use "classic theme" when running Layout tests

In order to pass Image layout tests on OS X, we need to set a bunch of system values.  These are only set if custom_theme is true.

BUG=42352
TEST=On OS X 10.5, compile test_shell and run webkit/tools/layout_tests/run_webkit_tests.sh --debug editing/selection/3690703.html , test should pass.

Review URL: http://codereview.chromium.org/3141037

git-svn-id: http://src.chromium.org/svn/trunk/src@57811 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 3032b0258477f16185b322f82d72d98bb417e576
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser