I'll roll up this change together with the patches from bug 766616 when uplifiting it to aurora https://hg.mozilla.org/integration/mozilla-inbound/rev/c4bb09009a54
Backed out in https://hg.mozilla.org/integration/mozilla-inbound/rev/9b9678df7672 because something in the push was hitting "browser_frameworker.js | sub-test testEarlyClose failed: [Exception... "Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIXPCComponents_Utils.nukeSandbox]" nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)" location: "JS frame :: resource://gre/modules/FrameWorker.jsm :: terminate :: line 239" data: no]" and "browser_frameworker.js | check that websockets worked - Got FAILED calling WebSocket constructor: TypeError: WebSocket is not a constructor, expected ok" and I didn't know which (though I presume bug 790201), and didn't know interconnectedness among them.
fixed in aurora with cset https://hg.mozilla.org/releases/mozilla-aurora/rev/b69ca3697450
Flagging [qa-] as I don't think this needs QA verification. Please correct me if I am wrong.