Port identity_internals to mojo

chrome/browser/ui/webui/identity_internals/identity_internals.mojom

+// Copyright 2014 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.
+
+struct IdentityTokenMojo {
+  string access_token;
+  string extension_name;
+  string extension_id;
+  string token_status;
+  string expiration_time;
+  string[] scopes;
+};
+
+[Client=InternalsPage]
+interface IdentityInternalsHandlerMojo {
+  GetTokens() => (IdentityTokenMojo[] tokens);
+  RevokeToken(string extension_id, string access_token) => ();
+};
+
+interface InternalsPage {
+};