Unskip 'http/tests/security/contentSecurityPolicy/object-src-none-blocked.html'

After contentshell, we don't seem to be leaking state here anymore. This patch
simply unskips the test.

R=jochen@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19176002

git-svn-id: svn://svn.chromium.org/blink/trunk@154223 bbb929c8-8fbe-4397-9dbb-9b2b20218538