phetsims/scenery-phet#71 let supertype handle touch area expansion, set default values for xTouchExpansion and yTouchExpansion that correspond to previous behavior of ArrowButton
phetsims/scenery-phet#71 let supertype handle touch area expansion, set default values for xTouchExpansion and yTouchExpansion that correspond to previous behavior of ArrowButton

phetsims/scenery-phet,phetsims/scenery-phet,phetsims/scenery-phet