dbus: Make Bus::GetManagedObjects skip unavailable services.

dbus/object_proxy.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DBUS_OBJECT_PROXY_H_
 #define DBUS_OBJECT_PROXY_H_
 
 #include <dbus/dbus.h>
 
 #include <map>
@@ skipping 160 matching lines @@
 
   // Sets a callback for "NameOwnerChanged" signal. The callback is called on
   // the origin thread when D-Bus system sends "NameOwnerChanged" for the name
   // represented by |service_name_|.
   virtual void SetNameOwnerChangedCallback(NameOwnerChangedCallback callback);
 
   // Runs the callback as soon as the service becomes available.
   virtual void WaitForServiceToBeAvailable(
       WaitForServiceToBeAvailableCallback callback);
 
+  // Returns true if the service is available (i.e. its name has an owner).
+  virtual bool ServiceIsAvailable();
+
   // Detaches from the remote object. The Bus object will take care of
   // detaching so you don't have to do this manually.
   //
   // BLOCKING CALL.
   virtual void Detach();
 
   const ObjectPath& object_path() const { return object_path_; }
 
   // Returns an empty callback that does nothing. Can be used for
   // CallMethod().
@@ skipping 133 matching lines @@
   std::string service_name_owner_;
 
   std::set<DBusPendingCall*> pending_calls_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectProxy);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_OBJECT_PROXY_H_