Make SignalSenderVerificationTest more robust

dbus/object_proxy.h

Index: dbus/object_proxy.h
diff --git a/dbus/object_proxy.h b/dbus/object_proxy.h
index bec08949d75b8d86d3cfec6a81f17ac5722e3415..eb40fd309d3b0abd247f70553bbb4d1bda482e9c 100644
--- a/dbus/object_proxy.h
+++ b/dbus/object_proxy.h
@@ -142,6 +142,11 @@ class CHROME_DBUS_EXPORT ObjectProxy
                                SignalCallback signal_callback,
                                OnConnectedCallback on_connected_callback);
 
+  // Sets a callback for "NameOwnerChanged" signal. The callback is called when
+  // D-Bus system sends "NameOwnerChanged" for the name represented by
+  // |service_name_|.
+  virtual void SetNameOwnerChangedCallback(SignalCallback callback);
+
   // Detaches from the remote object. The Bus object will take care of
   // detaching so you don't have to do this manually.
   //
@@ -268,6 +273,9 @@ class CHROME_DBUS_EXPORT ObjectProxy
   typedef std::map<std::string, SignalCallback> MethodTable;
   MethodTable method_table_;
 
+  // The callback called when NameOwnerChanged signal is received.
+  SignalCallback name_owner_changed_callback_;
+
   std::set<std::string> match_rules_;
 
   const bool ignore_service_unknown_errors_;