dbus: Rewrite ObjectProxy::ConnectToSignal with PostTaskAndReplyWithResult

dbus/object_proxy.h

Index: dbus/object_proxy.h
diff --git a/dbus/object_proxy.h b/dbus/object_proxy.h
index 798ba9711f3031ceb8599fcc68dc185b77cc919c..79e15d14bbc4f38a988b55a930c88bfecde6511d 100644
--- a/dbus/object_proxy.h
+++ b/dbus/object_proxy.h
@@ -204,17 +204,9 @@ class CHROME_DBUS_EXPORT ObjectProxy
                                            void* user_data);
 
   // Helper function for ConnectToSignal().
-  void ConnectToSignalInternal(
-      const std::string& interface_name,
-      const std::string& signal_name,
-      SignalCallback signal_callback,
-      OnConnectedCallback on_connected_callback);
-
-  // Called when the object proxy is connected to the signal, or failed.
-  void OnConnected(OnConnectedCallback on_connected_callback,
-                   const std::string& interface_name,
-                   const std::string& signal_name,
-                   bool success);
+  bool ConnectToSignalInternal(const std::string& interface_name,
+                               const std::string& signal_name,
+                               SignalCallback signal_callback);
 
   // Handles the incoming request messages and dispatches to the signal
   // callbacks.