cros: Make sure views-based lock screen is destroyed after it is dismissed.

chrome/browser/ui/ash/lock_screen_client.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_ASH_LOCK_SCREEN_CLIENT_H_
 #define CHROME_BROWSER_UI_ASH_LOCK_SCREEN_CLIENT_H_
 
 #include "ash/public/interfaces/lock_screen.mojom.h"
 #include "base/macros.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
-// Handles method calls delegated back to chrome from ash. Also notifies ash of
-// relevant state changes in chrome.
+// Handles method calls sent from ash to chrome. Also sends messages from chrome
+// to ash.
 class LockScreenClient : public ash::mojom::LockScreenClient {
  public:
   LockScreenClient();
   ~LockScreenClient() override;
 
   static LockScreenClient* Get();
 
   // ash::mojom::LockScreenClient:
   void AuthenticateUser(const AccountId& account_id,
                         const std::string& hashed_password,
-                        bool authenticated_by_pin) override;
+                        bool authenticated_by_pin,
+                        AuthenticateUserCallback callback) override;
 
   // Wrappers around the mojom::SystemTray interface.
+  void ShowLockScreen(ash::mojom::LockScreen::ShowLockScreenCallback on_shown);
   void ShowErrorMessage(int32_t login_attempts,
                         const std::string& error_text,
                         const std::string& help_link_text,
                         int32_t help_topic_id);
   void ClearErrors();
 
  private:
   // Lock screen mojo service in ash.
   ash::mojom::LockScreenPtr lock_screen_;
 
   // Binds this object to the client interface.
   mojo::Binding<ash::mojom::LockScreenClient> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(LockScreenClient);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_LOCK_SCREEN_CLIENT_H_