Stop propagating customscrollbar styles across iframe boundaries.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index db45beb8b718d176e75e4351537a0803dc379279..d2615f80f9de1b3fbc0455e4e97cb951a5ea2fc7 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -988,11 +988,6 @@ static inline const LayoutObject& layoutObjectForScrollbar(const LayoutObject& l
             Element* docElement = doc.documentElement();
             if (docElement && docElement->layoutObject() && docElement->layoutObject()->style()->hasPseudoStyle(PseudoIdScrollbar))
                 return *docElement->layoutObject();
-
-            // If we have an owning ipage/LocalFrame element, then it can set the custom scrollbar also.
-            LayoutPart* frameLayoutObject = node->document().frame()->ownerLayoutObject();
-            if (frameLayoutObject && frameLayoutObject->style()->hasPseudoStyle(PseudoIdScrollbar))
-                return *frameLayoutObject;
         }
 
         if (layoutObject.styleRef().hasPseudoStyle(PseudoIdScrollbar))