I did use CancelAndForgetObserver in the patch for bug 619899 (which basically does what my addon does, but implemented properly), but there's a comment in imgIRequest.idl saying that it shouldn't be used for new code.
I did use CancelAndForget Observer in the patch for bug 619899 (which basically does what my addon does, but implemented properly), but there's a comment in imgIRequest.idl saying that it shouldn't be used for new code.