ui: Fix clang warnings about missing virtual and OVERRIDE annotations.

ui/base/resource/resource_bundle.cc

Index: ui/base/resource/resource_bundle.cc
diff --git a/ui/base/resource/resource_bundle.cc b/ui/base/resource/resource_bundle.cc
index 5a2db84756fdfc9ed3a9ed5260d6ff9b3a3bf1ed..0071a5a22e871d41974e06be1cafcac6d8daca82 100644
--- a/ui/base/resource/resource_bundle.cc
+++ b/ui/base/resource/resource_bundle.cc
@@ -79,7 +79,8 @@ class ResourceBundle::ResourceBundleImageSource : public gfx::ImageSkiaSource {
   virtual ~ResourceBundleImageSource() {}
 
   // gfx::ImageSkiaSource overrides:
-  virtual gfx::ImageSkiaRep GetImageForScale(ui::ScaleFactor scale_factor) {
+  virtual gfx::ImageSkiaRep GetImageForScale(
+      ui::ScaleFactor scale_factor) OVERRIDE {
     ResourceBundle& rb = ResourceBundle::GetSharedInstance();
 
     scoped_ptr<SkBitmap> result(rb.LoadBitmap(resource_id_, scale_factor));