cros: Use SessionController for lock starting code

chrome/browser/chromeos/login/lock/webui_screen_locker.h

Index: chrome/browser/chromeos/login/lock/webui_screen_locker.h
diff --git a/chrome/browser/chromeos/login/lock/webui_screen_locker.h b/chrome/browser/chromeos/login/lock/webui_screen_locker.h
index fea1b725af96e579d7257b4e04397ee1cf7f67f2..bc61d9adb3af379a575e3d41fbf782ae892919ff 100644
--- a/chrome/browser/chromeos/login/lock/webui_screen_locker.h
+++ b/chrome/browser/chromeos/login/lock/webui_screen_locker.h
@@ -45,7 +45,6 @@ class WebUIScreenLockerTester;
 // Displays a WebUI lock screen based on the Oobe account picker screen.
 class WebUIScreenLocker : public WebUILoginView,
                           public LoginDisplay::Delegate,
-                          public ash::LockStateObserver,
                           public views::WidgetObserver,
                           public PowerManagerClient::Observer,
                           public display::DisplayObserver,
@@ -88,6 +87,9 @@ class WebUIScreenLocker : public WebUILoginView,
   // Called when the webui header bar becomes visible.
   void OnHeaderBarVisible();
 
+  // Called by ScreenLocker to notify that ash lock animation finishes.
+  void OnLockAnimationFinished();
+
  private:
   friend class test::WebUIScreenLockerTester;
 
@@ -119,9 +121,6 @@ class WebUIScreenLocker : public WebUILoginView,
   void Signout() override;
   bool IsUserWhitelisted(const AccountId& account_id) override;
 
-  // LockStateObserver:
-  void OnLockStateEvent(ash::LockStateObserver::EventType event) override;
-
   // WidgetObserver:
   void OnWidgetDestroying(views::Widget* widget) override;