User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:35.0) Gecko/20100101 Firefox/35.0 Build ID: 20140916030204 Steps to reproduce: Using Nightly: Open a new tab in existing window. Go to any webpage. Drag new tab outside current window to create a new window. (drag and drop) Ghost of old tab left behind in first window. Unable to close the ghost tab (in the first window). Actual results: The drag and drop tab (pointed at gmail) opened a new BLANK window (not pointed at gmail). Back in the former window, I cannot close the tab that I had dragged out. It's still pointing to the website that I went to and you can navigate within the window, but I cannot close that tab. Expected results: The drag and drop should have opened the current webpage in a NEW window. Back in the former window, the tab would be absent. (A move instead of a duplicate - which wasn't even a duplicate because it opened a new blank window)

Can reproduce.