Bug 1132566 - Enable test in e10s: browser_privatebrowsing_DownloadLastDirWithCPS.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 : 255322b4277cd045d7f8556b7f98c7d78320961b

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

@@ -16,7 +16,6 @@ support-files =
   title.sjs
 
 [browser_privatebrowsing_DownloadLastDirWithCPS.js]
-skip-if = e10s
 [browser_privatebrowsing_aboutHomeButtonAfterWindowClose.js]
 skip-if = true # Bug 1142678 - Loading a message sending frame script into a private about:home tab causes leaks
 [browser_privatebrowsing_aboutHomeButtonAfterWindowClose_old.js]