Update {virtual,override} to follow C++11 style in ui.

ui/events/event_target_iterator.h

Index: ui/events/event_target_iterator.h
diff --git a/ui/events/event_target_iterator.h b/ui/events/event_target_iterator.h
index 28b4a30202a3fa2e29d1f32520188f2ac5bb06cb..fe3eca6c1730b39b2a2d69e1089a5dafd3b99a77 100644
--- a/ui/events/event_target_iterator.h
+++ b/ui/events/event_target_iterator.h
@@ -28,9 +28,9 @@ class EventTargetIteratorImpl : public EventTargetIterator {
       : begin_(children.rbegin()),
         end_(children.rend()) {
   }
-  virtual ~EventTargetIteratorImpl() {}
+  ~EventTargetIteratorImpl() override {}
 
-  virtual EventTarget* GetNextTarget() override {
+  EventTarget* GetNextTarget() override {
     if (begin_ == end_)
       return NULL;
     EventTarget* target = *(begin_);