Implement Web Restrictions in WebView.

components/web_restrictions/interfaces/web_restrictions.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 web_restrictions.mojom;
+
+struct ClientResult {
+  map<string, int32> intParams;
+  map<string, string> stringParams;
+};
+
+interface WebRestrictions {
+  // Get the cached result, if any, of requesting access to a URL; including key/value pairs for
+  // custom error ints and strings. This has to be synchronous since it is needed to show the error
+  // page, and delaying the error page can result in a race with the Webview API.
+  [Sync]
+  GetResult(string url) => (ClientResult? reply);
+
+  // Request 
+  RequestPermission(string url) => (bool result);
+};