from https://bugzilla.mozilla.org/show_bug.cgi?id=770679#c2: """ I do not understand why would you need these __exposedProps__ here and elsewhere. This code should live in the sandbox and sandbox should have a content principal (not a priviledged/chrome one). We end up calling workerWindow.postMessage, which should be a using exactly same principal and still a content one. I thought __exposedProps__ was only used for chrome objects exposed to content. """ Note however that some __exposedProps__ probably *will* need to remain - eg, the "client port" is used by, eg, the sidebar content, but it probably can be removed from the "worker port". I intent to not bother with this until some UI pieces land, so the client ports are better exercised and we can get a more definitive answer on which ones are necessary and which ones are not.

I think we've removed all of the unnecessary uses of __exposedProps__ - the two I see left in FrameWorker.jsm seem to be required (since they're content-exposed chrome objects).

I agree - only those necessary remain.