Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/modules/quota/StorageManager.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.
 
 // https://storage.spec.whatwg.org/#storagemanager
 
 enum PersistentStoragePermission { "default", "denied", "granted" };
 
 [
     Exposed=(Window,Worker),
-    GarbageCollected,
     RuntimeEnabled=DurableStorage,
 ] interface StorageManager {
     [Exposed=Window, CallWith=ScriptState] Promise<boolean> requestPersistent();
     [CallWith=ScriptState] Promise<PersistentStoragePermission> persistentPermission();
 
     // TODO(dgrogan): Implement estimate() and persistentEstimate().
 };