The show() function should be updated to handle putting the view in the DOM instead of the view object handling it. Show should ensure the provided fragment is translated and that it is still the currently shown view before doing so.
Without this a view taking a long time to load can replace a view that is later loaded.
This bug is preventing toolkit/mozapps/extensions/test/browser/browser_bug562899.js from being run with HTML about:addons enabled.
The test has been marked as XUL-only for now in https://phabricator.services.mozilla.com/D31789 ; we should update the test for HTML about:addons before closing this bug.