ObserverList::HasObserver now takes a const pointer.

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index 4f597eb8a85a2c344292772b0dd825098de31229..d1cff7b8049994e36da8a15db7dac87b3434b498 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -223,7 +223,7 @@ class AURA_EXPORT Window : public ui::LayerDelegate,
   // Add/remove observer.
   void AddObserver(WindowObserver* observer);
   void RemoveObserver(WindowObserver* observer);
-  bool HasObserver(WindowObserver* observer);
+  bool HasObserver(const WindowObserver* observer) const;
 
   void set_ignore_events(bool ignore_events) { ignore_events_ = ignore_events; }
   bool ignore_events() const { return ignore_events_; }