Still broken, this time because PagedOutlineLayout / BookletLayout
usage wasn't updated.
This reverts commit c6cfe763bb.
Change-Id: If0d37d396ecf3bb09f026d4432c5d7e30f040085
Also, as OOjs UI's StackPanelLayout was renamed to StackLayout, and the
showItem() function to setItem(), fix uses in VisualEditor.
Change-Id: If153e5e7c3a7c60e3d62e20aac8fabd4eaaa73c2