mojo api for view based lockscreen

ash/public/interfaces/lock_screen.mojom

Index: ash/public/interfaces/lock_screen.mojom
diff --git a/ash/public/interfaces/lock_screen.mojom b/ash/public/interfaces/lock_screen.mojom
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+// Copyright 2017 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 ash.mojom;
+
+import "components/signin/public/interfaces/account_id.mojom";
+
+// Allows clients (e.g. Chrome browser) to control the ash lock screen.
+interface LockScreen {
+  // Sets the client interface.
+  SetClient(LockScreenClient client);
+
+  // Shows error message in the ash lock screen.
+  ShowErrorMessage();
+};
+
+// Allows ash lock screen to control a client (e.g. Chrome browser). Requests
+// often involve preferences or talk to cryptohome that is not available to ash.
+interface LockScreenClient {
+  // Request user authentication in chrome. 
+  AuthenticateUser(signin.mojom.AccountId account_id, string password, bool authenticated_by_pin);
+};