[Background Sync] Converting Blink code to the MVP API

Source/modules/background_sync/SyncRegistration.idl

 // Copyright 2015 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.
 
 [
     Exposed=(Window,ServiceWorker),
     GarbageCollected,
     RuntimeEnabled=BackgroundSync,
 ] interface SyncRegistration {
-    readonly attribute DOMString id;
-    readonly attribute unsigned long minDelay;
-    readonly attribute unsigned long maxDelay;
-    readonly attribute unsigned long minPeriod;
-    readonly attribute SyncNetworkType minRequiredNetwork;
-    readonly attribute boolean allowOnBattery;
-    readonly attribute boolean idleRequired;
+    [RuntimeEnabled=BackgroundSyncV2] readonly attribute DOMString tag;
     [CallWith=ScriptState] Promise<boolean> unregister();
 };