drawerhost DrawerClosing event only work when close one drawer by use command

when click other place to close drawer or use close all drawer command
the DrawerClosing event doesn't work

Start by reproducing the DrawerHost behavior when clicking elsewhere and when using the close-all-drawer command, then inspect how DrawerClosing is raised for each close path. Done means the DrawerClosing event fires consistently for closing one drawer, clicking elsewhere, and closing all drawers.

Written by the indexing model from the issue text.