Comment 0 for bug 61182

When you build with --enable-chrome-format=flat, feeds subscription dialog is broken due to FileWriter._isValidWindow function checking that the real URL of the page called into it starts with "jar:file://", which is obviously not true for a app built with flat chrome.

I'm going to change that check to a more restrictive, but at the same time more correct: check that the real URI of the page equals the resolved URI returned by the chrome registry for the subscription page (chrome://browser/content/feeds/subscribe.xhtml)