Steps to Reproduce

	<hbox height="100px" width="100%">
		<div/>
		<splitter collapse="before"/>
		<div/>
	</hbox>
	<hbox height="100px" width="100%">
		<div/>
		<splitter collapse="after"/>
		<div>
	</hbox>

check aria-controls attribute is pointing a the primary pane (the one that's going to collapse on click)

Current Result

in the bottom case aria-controls still points to the left side

Expected Result

aria-controls must point to the primary panel which is the left for "before" and the right for "after"

Debug Information

Workaround