Fix issue #1401973 and #2111181 (menu placement problems).

Issue 1401973: A dialog with menu has wrong menu placement
Issue 2111181: status bar overlaps the more menu in browser

Menus are now dialog panels, so they are placed within the entire
screen and not attached to their parent window.

Change-Id: Ia9702d5e30a6ba5ebb0254abe6a94cbbdfa9866d