Constify and use LayoutStyle reference in layout/

Source/core/layout/LayoutTableCell.h

Index: Source/core/layout/LayoutTableCell.h
diff --git a/Source/core/layout/LayoutTableCell.h b/Source/core/layout/LayoutTableCell.h
index 2a5859495bd9c23d58932df3fb39c1c155c1ae0b..d3c94271aee47a99368ae9954970b66907b09c43 100644
--- a/Source/core/layout/LayoutTableCell.h
+++ b/Source/core/layout/LayoutTableCell.h
@@ -171,9 +171,9 @@ public:
     // This means we can safely use the same style in all cases to simplify our code.
     // FIXME: Eventually this function should replaced by style() once we support direction
     // on all table parts and writing-mode on cells.
-    const LayoutStyle* styleForCellFlow() const
+    const LayoutStyle& styleForCellFlow() const
     {
-        return row()->style();
+        return row()->styleRef();
     }
 
     const BorderValue& borderAdjoiningTableStart() const