Is a paper-action-dialog supposed to automatically center and scroll with dart-polymer? -

i trying launch modal dialog using paperactiondialog in dart , dialog never centers , doesn't scroll if content longer window. supposed automatically? polymer-only examples come across seem to. have style somehow? here's code i'm using:

paperactiondialog m = new paperactiondialog(); m.setattribute("role", "dialog"); m.setattribute("backdrop", "true"); m.autoclosedisabled=true; paperbutton closebutton = new paperbutton(); closebutton.text="close"; closebutton.raised = true; closebutton.setattribute("primary", "true"); closebutton.setattribute("dismissive", "true"); m.children.add(closebutton); m.heading="history"; m.open();