Clean-up proxy_service_unittest.cc, to remove dependency on SingleThreadedProxyResolver.
Clean-up proxy_service_unittest.cc, to remove dependency on SingleThreadedProxyResolver.

This was a TODO generated in <http://codereview.chromium.org/149525>

This simplifies the test code since everything is running on one thread.

BUG=http://crbug.com/11746, http://crbug.com/11079

Review URL: http://codereview.chromium.org/160155

git-svn-id: http://src.chromium.org/svn/trunk/src@21829 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: c4836aec5f5652dfead2c46f984e9086ea93205f
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