Update rendering classes to use OVERRIDE / FINAL when needed

Source/core/rendering/RenderMultiColumnBlock.h

Index: Source/core/rendering/RenderMultiColumnBlock.h
diff --git a/Source/core/rendering/RenderMultiColumnBlock.h b/Source/core/rendering/RenderMultiColumnBlock.h
index ac92d2f9ff927dfbed292ddf7d0967a4fe238ed4..cdcf00b6f94125fa2942fbbfe8d7dcb97e0701e9 100644
--- a/Source/core/rendering/RenderMultiColumnBlock.h
+++ b/Source/core/rendering/RenderMultiColumnBlock.h
@@ -47,9 +47,9 @@ public:
     bool requiresBalancing() const { return !m_columnHeightAvailable || style()->columnFill() == ColumnFillBalance; }
 
 private:
-    virtual bool isRenderMultiColumnBlock() const { return true; }
+    virtual bool isRenderMultiColumnBlock() const OVERRIDE { return true; }
 
-    virtual const char* renderName() const;
+    virtual const char* renderName() const OVERRIDE;
 
     virtual RenderObject* layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope&) OVERRIDE;