[Background Sync] Allow sync manager access from uncontrolled clients

Source/modules/background_sync/SyncManager.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.
 
 enum SyncPermissionState {
   "default",
   "denied",
   "granted"
 };
 
 [
     Exposed=(Window,ServiceWorker),
     GarbageCollected,
     RuntimeEnabled=BackgroundSync,
     TypeChecking=Interface,
 ] interface SyncManager {
-    [CallWith=ScriptState,ImplementedAs=registerFunction] Promise<SyncRegistration> register([RuntimeEnabled=BackgroundSyncV2] optional SyncRegistrationOptions options);
+    [CallWith=(ScriptState,ExecutionContext),ImplementedAs=registerFunction] Promise<SyncRegistration> register([RuntimeEnabled=BackgroundSyncV2] optional SyncRegistrationOptions options);
     [CallWith=ScriptState] Promise<SyncRegistration> getRegistration(DOMString tag);
     [CallWith=ScriptState] Promise<sequence<SyncRegistration>> getRegistrations();
     [RuntimeEnabled=BackgroundSyncV2, CallWith=ScriptState] Promise<SyncPermissionState> permissionState();
 };