Bug 1132566 - Enable test in e10s: browser_privatebrowsing_ui.js; r=billm

This test appeared to run fine under e10s, so after running 30 times
with "mochitest-browser --e10s --run-until-failure" I've re-enabled it.

--HG--
extra : rebase_source : 7b63db65f319cec51783349bd0597c0926549222

browser/components/privatebrowsing/test/browser/browser.ini

@@ -45,7 +45,6 @@ skip-if = e10s # Bug 940206 -  nsIWebContentHandlerRegistrar::registerProtocolHa
 [browser_privatebrowsing_sidebar.js]
 [browser_privatebrowsing_theming.js]
 [browser_privatebrowsing_ui.js]
-skip-if = e10s
 [browser_privatebrowsing_urlbarfocus.js]
 skip-if = e10s
 [browser_privatebrowsing_windowtitle.js]