In legacy/trac#9881 (moved) we switched
0 as a stopgap to a possible screen size leak. This solution has the disadvantage that all popup windows get added as a new tab which is at least unexpected to the user. What we want is a patch that retains the old behavior (i.e. a popup window gets opened/resized and not added as a tab) while the screen/outerWindow dimensions are still not being leaked.