--- a/layout/xul/nsSliderFrame.cpp
+++ b/layout/xul/nsSliderFrame.cpp
@@ -328,17 +328,16 @@ nsSliderFrame::BuildDisplayListForChildr
     // attach scrolling information to it.
     // We do this here and not in the thumb's nsBoxFrame::BuildDisplayList so
     // that the event region that gets created for the thumb is included in
     // the nsDisplayOwnLayer contents.
 
     uint32_t flags = 0;
     mozilla::layers::FrameMetrics::ViewID scrollTargetId =
       mozilla::layers::FrameMetrics::NULL_SCROLL_ID;
-    float scrollbarThumbRatio = 0.0f;
     aBuilder->GetScrollbarInfo(&scrollTargetId, &flags);
     bool thumbGetsLayer = (scrollTargetId != layers::FrameMetrics::NULL_SCROLL_ID);
     nsLayoutUtils::SetScrollbarThumbLayerization(thumb, thumbGetsLayer);
 
     if (thumbGetsLayer) {
       nsDisplayListCollection tempLists;
       nsBoxFrame::BuildDisplayListForChildren(aBuilder, aDirtyRect, tempLists);
 
@@ -350,17 +349,17 @@ nsSliderFrame::BuildDisplayListForChildr
       masterList.AppendToTop(tempLists.Floats());
       masterList.AppendToTop(tempLists.Content());
       masterList.AppendToTop(tempLists.PositionedDescendants());
       masterList.AppendToTop(tempLists.Outlines());
 
       // Wrap the list to make it its own layer.
       aLists.Content()->AppendNewToTop(new (aBuilder)
         nsDisplayOwnLayer(aBuilder, this, &masterList, flags, scrollTargetId,
-                          scrollbarThumbRatio));
+                          GetThumbRatio()));
 
       return;
     }
   }
   
   nsBoxFrame::BuildDisplayListForChildren(aBuilder, aDirtyRect, aLists);
 }