Add Notification.maxActions so websites know how many buttons we support

Source/modules/notifications/Notification.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 276 matching lines @@
 }
 
 void Notification::requestPermission(ExecutionContext* context, NotificationPermissionCallback* callback)
 {
     // FIXME: Assert that this code-path will only be reached for Document environments
     // when Blink supports [Exposed] annotations on class members in IDL definitions.
     if (NotificationPermissionClient* permissionClient = NotificationPermissionClient::from(context))
         permissionClient->requestPermission(context, callback);
 }
 
+unsigned Notification::maxActions()
+{
+    return notificationManager()->maxActions();
+}
+
 bool Notification::dispatchEventInternal(PassRefPtrWillBeRawPtr<Event> event)
 {
     ASSERT(executionContext()->isContextThread());
     return EventTarget::dispatchEventInternal(event);
 }
 
 const AtomicString& Notification::interfaceName() const
 {
     return EventTargetNames::Notification;
 }
@@ skipping 20 matching lines @@
     return ScriptValue(scriptState, m_serializedData->deserialize(scriptState->isolate()));
 }
 
 DEFINE_TRACE(Notification)
 {
     RefCountedGarbageCollectedEventTargetWithInlineData<Notification>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink