ObserverList::HasObserver now takes a const pointer.

ui/wm/core/user_activity_detector.cc

Index: ui/wm/core/user_activity_detector.cc
diff --git a/ui/wm/core/user_activity_detector.cc b/ui/wm/core/user_activity_detector.cc
index 56bf563b3d032f11b34b87a5af295b78f11c4b7e..8263460f8927a18e348c9469728ef2f35d794630 100644
--- a/ui/wm/core/user_activity_detector.cc
+++ b/ui/wm/core/user_activity_detector.cc
@@ -49,7 +49,8 @@ UserActivityDetector::UserActivityDetector() {
 UserActivityDetector::~UserActivityDetector() {
 }
 
-bool UserActivityDetector::HasObserver(UserActivityObserver* observer) const {
+bool UserActivityDetector::HasObserver(
+    const UserActivityObserver* observer) const {
   return observers_.HasObserver(observer);
 }