Gtk: Fix leaking style objects when using gtk theme.
Gtk: Fix leaking style objects when using gtk theme.

TEST=run a ui test under valgrind
BUG=none

Review URL: http://codereview.chromium.org/4794001

git-svn-id: http://src.chromium.org/svn/trunk/src@65768 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 49f0d876836df58f6b2f4281ee3cb68e638f2363
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