There was support for an MOD2+drag operation in ToolBox, apparently intended to
allow customization by re-arranging items.  However, in
ImplTBDragMgr::EndDragging that operation would always have ended in doing
nothing:  Ever since at least 8ab086b6 "initial
import", what happened was a call to virtual ToolBox::Customize, but which had
an empty body and wasn't overridden anywhere (and has since been cleaned away
over a series of commits).

Change-Id: I8c5962d7b29506dc7dc8d803f49847f30fb93ea1