ObserverList::HasObserver now takes a const pointer.

chromeos/dbus/fake_update_engine_client.cc

Index: chromeos/dbus/fake_update_engine_client.cc
diff --git a/chromeos/dbus/fake_update_engine_client.cc b/chromeos/dbus/fake_update_engine_client.cc
index 53314e2381e36830d44f8cc818883f6302e3d486..a594a3e1e6d712d11af0ed1a19ea2577e5688c8c 100644
--- a/chromeos/dbus/fake_update_engine_client.cc
+++ b/chromeos/dbus/fake_update_engine_client.cc
@@ -29,7 +29,7 @@ void FakeUpdateEngineClient::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
-bool FakeUpdateEngineClient::HasObserver(Observer* observer) {
+bool FakeUpdateEngineClient::HasObserver(const Observer* observer) const {
   return observers_.HasObserver(observer);
 }