We need a way to disable specific or all site patches, so developers and WebCompat testers (and, FWIW, test suites) are able to test the raw site. Also, we need to discuss if we need a UI to disable specific patches or if it's good enough to have a preference to disable everything.

Also, we need to think about whether disabling patches should be permanent or if everything should be disabled after a browser restart.

Eric, I implemented a basic preference called `extensions.webcompat.perform_ua_overrides` to turn all overrides off. As discussed, this resets on every browser start.

Comment on attachment 8803270 [details] PR to implement a preference to turn everything off Please see my comments in PR.

Comment on attachment 8803270 [details] PR to implement a preference to turn everything off Thanks for fixing the observer.

r+ from Eric as discussed per email[0]. If we run into troubles for forcing the pref to true when merging it into central, we can reconsider this decision, but for now, this is fine. [0]: https://groups.google.com/forum/#!topic/mozilla.compatibility/tlwuFzZfz2o

Merged.