Switch DPLStackingNode to use LayoutBoxModelObject

Source/core/paint/DeprecatedPaintLayer.cpp

Index: Source/core/paint/DeprecatedPaintLayer.cpp
diff --git a/Source/core/paint/DeprecatedPaintLayer.cpp b/Source/core/paint/DeprecatedPaintLayer.cpp
index 35816c7fce8fc8f7916048454bae7897b8e2df9d..cf2d8e252d81c335a87107d0bfac5b15d1cc689f 100644
--- a/Source/core/paint/DeprecatedPaintLayer.cpp
+++ b/Source/core/paint/DeprecatedPaintLayer.cpp
@@ -1432,7 +1432,7 @@ void DeprecatedPaintLayer::updateReflectionInfo(const ComputedStyle* oldStyle)
 void DeprecatedPaintLayer::updateStackingNode()
 {
     if (requiresStackingNode())
-        m_stackingNode = adoptPtr(new DeprecatedPaintLayerStackingNode(this));
+        m_stackingNode = adoptPtr(new DeprecatedPaintLayerStackingNode(*layoutObject()));
     else
         m_stackingNode = nullptr;
 }
@@ -1606,12 +1606,6 @@ Node* DeprecatedPaintLayer::enclosingElement() const
     return 0;
 }
 
-bool DeprecatedPaintLayer::isInTopLayer() const
-{
-    Node* node = layoutObject()->node();
-    return node && node->isElementNode() && toElement(node)->isInTopLayer();
-}
-
 // Compute the z-offset of the point in the transformState.
 // This is effectively projecting a ray normal to the plane of ancestor, finding where that
 // ray intersects target, and computing the z delta between those two points.