dbus: Make Bus::GetManagedObjects skip unavailable services.

dbus/object_proxy.h

Index: dbus/object_proxy.h
diff --git a/dbus/object_proxy.h b/dbus/object_proxy.h
index 033e88608a095234d568eb559f09471ef0fa0b00..7747374c58a23a4f1a496aa8732c82fd2f046a25 100644
--- a/dbus/object_proxy.h
+++ b/dbus/object_proxy.h
@@ -178,6 +178,9 @@ class CHROME_DBUS_EXPORT ObjectProxy
   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.
   //