Enforce marking "override" for functions overriding Blink.

content/child/webthemeengine_impl_default.h

Index: content/child/webthemeengine_impl_default.h
diff --git a/content/child/webthemeengine_impl_default.h b/content/child/webthemeengine_impl_default.h
index a05313aad986f701a1a2ca72459005b163e094ce..df2523812a5fae09f71e3532f029fead3c9501ad 100644
--- a/content/child/webthemeengine_impl_default.h
+++ b/content/child/webthemeengine_impl_default.h
@@ -12,13 +12,12 @@ namespace content {
 class WebThemeEngineImpl : public blink::WebThemeEngine {
  public:
   // WebThemeEngine methods:
-  virtual blink::WebSize getSize(blink::WebThemeEngine::Part);
-  virtual void paint(
-      blink::WebCanvas* canvas,
-      blink::WebThemeEngine::Part part,
-      blink::WebThemeEngine::State state,
-      const blink::WebRect& rect,
-      const blink::WebThemeEngine::ExtraParams* extra_params);
+  blink::WebSize getSize(blink::WebThemeEngine::Part) override;
+  void paint(blink::WebCanvas* canvas,
+             blink::WebThemeEngine::Part part,
+             blink::WebThemeEngine::State state,
+             const blink::WebRect& rect,
+             const blink::WebThemeEngine::ExtraParams* extra_params) override;
   virtual void paintStateTransition(blink::WebCanvas* canvas,
                                     blink::WebThemeEngine::Part part,
                                     blink::WebThemeEngine::State startState,