ui/DropDownMenu: use mergeInto to prepare for createClass.  fixed sizeAndCenter() to take into account padding of top item and center on .topItem, since that is what the offset will be off of !BUGFIX !STYLEGUIDE
ui/DropDownMenu: use mergeInto to prepare for createClass.  fixed sizeAndCenter() to take into account padding of top item and center on .topItem, since that is what the offset will be off of
!BUGFIX !STYLEGUIDE
tobymackenzie/Web-ClientBehavior,tobymackenzie/Web-ClientBehavior