use device gray for edges of BDSKEdgeView, looks more like edge colors used by NSScrollView
use device gray for edges of BDSKEdgeView, looks more like edge colors used by NSScrollView

JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim