Don't include LayoutObject-derived headers where not needed.

third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp

Index: third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp b/third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp
index 5e70a18b98b7b7de7221a9b8da437ff9ac88743b..4940df7bb9d775466499d6dbfeb1b5966f1e3027 100644
--- a/third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/RootScrollerUtil.cpp
@@ -7,8 +7,7 @@
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/frame/FrameView.h"
-#include "core/layout/LayoutBox.h"
-#include "core/layout/LayoutObject.h"
+#include "core/layout/LayoutBoxModelObject.h"
 #include "core/paint/PaintLayerScrollableArea.h"
 
 namespace blink {
@@ -31,7 +30,7 @@ ScrollableArea* scrollableAreaFor(const Element& element) {
     return nullptr;
 
   return static_cast<PaintInvalidationCapableScrollableArea*>(
-      toLayoutBox(element.layoutObject())->getScrollableArea());
+      toLayoutBoxModelObject(element.layoutObject())->getScrollableArea());
 }
 
 }  // namespace RootScrollerUtil