cros: Initial structure for views-based lock.

ash/login/views/lock_screen.cc

+// 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.
+
+#include "ash/login/views/lock_screen.h"
+
+#include "ash/login/views/contents_view.h"
+#include "ash/public/interfaces/constants.mojom.h"
+#include "ash/public/interfaces/session_controller.mojom.h"
+#include "ash/shell.h"
+#include "ash/shell_delegate.h"
+#include "services/service_manager/public/cpp/connector.h"
+#include "ui/views/widget/widget.h"
+
+namespace ash {
+
+void ShowLockScreenInWidget(views::Widget* widget) {
+  views::View* contents = new ContentsView();
+  widget->SetContentsView(contents);
+  widget->Show();
+
+  // Lock screen has been displayed; upate session state so we do not timeout
+  // and crash.
+  ash::mojom::SessionInfoPtr info = ash::mojom::SessionInfo::New();
+  info->state = session_manager::SessionState::LOCKED;
+  ash::mojom::SessionControllerPtr session_controller;
+  ash::Shell::Get()->shell_delegate()->GetShellConnector()->BindInterface(
+      ash::mojom::kServiceName, &session_controller);
+  session_controller->SetSessionInfo(std::move(info));

[xiyuan, 2017/05/08 17:11:50]

In current code, the session state code originates only from browser, managed by
session manager component. As the code is put under ash/, it should run in ash.
We would need a mojo call back to browser to update the session state source.

Is the reason why we need to put the code under ash/? If so, this does not look
like a good reason. The UI code might not need to talk to ash directly. Depends
on where the code runs, if we run the code in browser, it could talk to session
manager component, similar to what we have today.

[jdufault, 2017/05/08 20:46:51]

Done; discussed offline. login will stay in ash with high-level mojo API calls
to browser (ie, lockScreen, like what we have now with chrome.send). session
manager logic stays in browser.

+}
+
+}  // namespace ash