cros: Preload and reuse the lock screen across lock sessions

chrome/browser/chromeos/login/session/chrome_session_manager.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_CHROME_SESSION_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_CHROME_SESSION_MANAGER_H_
 
 #include "base/macros.h"
 #include "components/session_manager/core/session_manager.h"
 
 namespace base {
 class CommandLine;
 }
 
 class Profile;
 
 namespace chromeos {
 
+class IdleDetector;
+
 class ChromeSessionManager : public session_manager::SessionManager {
  public:
   ChromeSessionManager();
   ~ChromeSessionManager() override;
 
   // Initialize session manager on browser starts up. Runs different code
   // path based on command line flags and policy. Possible scenarios include:
   //   - Launches pre-session UI such as  out-of-box or login;
   //   - Launches the auto launched kiosk app;
   //   - Resumes user sessions on crash-and-restart;
   //   - Starts a stub login session for dev or test;
   void Initialize(const base::CommandLine& parsed_command_line,
                   Profile* profile,
                   bool is_running_test);
 
   // session_manager::SessionManager:
   void SessionStarted() override;
   void NotifyUserLoggedIn(const AccountId& user_account_id,
                           const std::string& user_id_hash,
                           bool browser_restart) override;
 
  private:
+  // Used to preload the lock screen when the user is inactive.
+  std::unique_ptr<IdleDetector> idle_detector_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeSessionManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_CHROME_SESSION_MANAGER_H_