Some random Web Notification cleanups

Source/modules/notifications/NotificationPermissionClient.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "modules/notifications/NotificationPermissionClient.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/LocalFrame.h"
 
 namespace blink {
 
 const char* NotificationPermissionClient::supplementName()
 {
     return "NotificationPermissionClient";
 }
 
 NotificationPermissionClient* NotificationPermissionClient::from(ExecutionContext* context)
 {
     if (!context->isDocument())
-        return 0;
+        return nullptr;
 
     const Document* document = toDocument(context);
     if (!document->frame() || !document->frame()->isLocalFrame())
-        return 0;
+        return nullptr;
 
     return static_cast<NotificationPermissionClient*>(WillBeHeapSupplement<LocalFrame>::from(document->frame(), supplementName()));
 }
 
 void provideNotificationPermissionClientTo(LocalFrame& frame, PassOwnPtrWillBeRawPtr<NotificationPermissionClient> client)
 {
     frame.provideSupplement(NotificationPermissionClient::supplementName(), client);
 }
 
 }