Introduce the Blink NotificationService, move permission checks there

third_party/WebKit/public/platform/modules/notifications/notification_service.mojom

+// Copyright 2016 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.
+
+module blink.mojom;
+
+import "third_party/WebKit/public/platform/modules/permissions/permission_status.mojom";
+
+// Service through which Blink can request notifications to be shown, closed or
+// retrieved from the embedder.
+interface NotificationService {
+  // Synchronously retrieves the permission status for |origin|. Required to
+  // be synchronous due to the Notification.permission JavaScript getter.
+  [Sync] GetPermissionStatus(string origin) => (PermissionStatus status);
+};