ObserverList::HasObserver now takes a const pointer.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index fb297685414e04402b453b92522789345f8852f8..e6dde9cdeefdd1a51459b0a29265adb2c2c4d941 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -216,11 +216,11 @@ class COMPOSITOR_EXPORT Compositor
   // observer to remove itself when it is done observing.
   void AddObserver(CompositorObserver* observer);
   void RemoveObserver(CompositorObserver* observer);
-  bool HasObserver(CompositorObserver* observer);
+  bool HasObserver(const CompositorObserver* observer) const;
 
   void AddAnimationObserver(CompositorAnimationObserver* observer);
   void RemoveAnimationObserver(CompositorAnimationObserver* observer);
-  bool HasAnimationObserver(CompositorAnimationObserver* observer);
+  bool HasAnimationObserver(const CompositorAnimationObserver* observer) const;
 
   // Creates a compositor lock. Returns NULL if it is not possible to lock at
   // this time (i.e. we're waiting to complete a previous unlock).