Expose Durable Storage API to script

Source/modules/quota/StorageManager.idl

Index: Source/modules/quota/StorageManager.idl
diff --git a/Source/modules/quota/StorageManager.idl b/Source/modules/quota/StorageManager.idl
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+// 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),
+    TypeChecking=Interface,
+    GarbageCollected,
+    RuntimeEnabled=DurableStorage,
+] interface StorageManager {
+    [CallWith=ScriptState] Promise<PersistentStoragePermission> requestPersistent();
+    [CallWith=ScriptState] Promise<PersistentStoragePermission> persistentPermission();
+
+    // TODO(dgrogan): Implement estimate() and persistentEstimate().
+};