User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20130219 Firefox/20.0 Build ID: 20130219042021 Steps to reproduce: Set Windows DPI to something high like 150 or 200% Set the layout.css.devPixelsPerPx value to -1.0 Click a link handled by an external protocol. The mailto: links in Bugzilla are a convenient choice. Actual results: Observe that the external protocol dialog is in the lower right corner of the screen. Expected results: It should be in the middle of the screen or parent window.
This is the same underlying issue as bug 844857, just using a different window to exhibit the behavior.