#7 Breaks testpilot extensions

It seems this addon also breaks [testpilot](https://testpilot.firefox.com/experiments/) extension. Here an error list: * [it completly breaks pageshot](https://github.com/mozilla-services/pageshot/issues/1700) * [it hides the Min Vid ico](https://github.com/meandavejustice/min-vid/issues/394)

@desktopd See [this reply](https://github.com/meandavejustice/min-vid/issues/394#issuecomment-252693093) on GitHub: > We are serving the min-vid icon from resource://. As far as I'm aware, serving icons from resource:// seems to be the standard for add ons. Do you know any better way to serve icons?

I'm very sorry, but the problem is that there's no way to restrict websites without restricting add-ons. Our add-on tries to prevent websites from reading the user's browser resources, but any add-ons that try to load such resources into content frames are needlessly affected. That's a design restriction of Firefox. Please also see _[[Proposal] Isolated content environment](https://discourse.mozilla-community.org/t/proposal-isolated-content-environment/9866)_ and _[How to determine the MIME type of the loading document in a Content Policy](https://discourse.mozilla-community.org/t/how-to-determine-the-mime-type-of-the-loading-document-in-a-content-policy/9917)_. (If you have any clue to the problem, I'll appreciate it.) Additionally, though I don't generally recommend it, users can expose certain resources by resource domain name with a setting.