Fix shift-action modifier in context menu
Before this patch, the shift-action modifier in context menus did not work when a sub-context menu is open, that does not have the main context menu as its parent. The new fix installs an event filter on QApplication whenever a new context menu is opened to make the context menu aware of shift-presses even when a sub-context menu is in focus. BUG: 425997 FIXED-IN: 21.04