Update more core classes to use OVERRIDE / FINAL when needed

Source/core/rendering/RenderFullScreen.cpp

Index: Source/core/rendering/RenderFullScreen.cpp
diff --git a/Source/core/rendering/RenderFullScreen.cpp b/Source/core/rendering/RenderFullScreen.cpp
index 23fa9925c0ffcc94ee92624e5cb9b440e92b4dc9..6e778045c022c9724cd99aa888ab0f862f9dba80 100644
--- a/Source/core/rendering/RenderFullScreen.cpp
+++ b/Source/core/rendering/RenderFullScreen.cpp
@@ -39,9 +39,9 @@ public:
         setDocumentForAnonymous(&owner->document());
     }
 private:
-    virtual bool isRenderFullScreenPlaceholder() const { return true; }
+    virtual bool isRenderFullScreenPlaceholder() const OVERRIDE { return true; }
     virtual bool supportsPartialLayout() const OVERRIDE { return false; }
-    virtual void willBeDestroyed();
+    virtual void willBeDestroyed() OVERRIDE;
     RenderFullScreen* m_owner;
 };