cros: Use SessionController for lock starting code

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

Index: chrome/browser/chromeos/login/lock/screen_locker.h
diff --git a/chrome/browser/chromeos/login/lock/screen_locker.h b/chrome/browser/chromeos/login/lock/screen_locker.h
index 07f65bb99bebfc0f465796f9d8d9d493c1595022..e15ecd6464c44cf7b4568435a9fc875b5e8a486a 100644
--- a/chrome/browser/chromeos/login/lock/screen_locker.h
+++ b/chrome/browser/chromeos/login/lock/screen_locker.h
@@ -145,6 +145,11 @@ class ScreenLocker : public AuthStatusConsumer {
   // Looks up user in unlock user list.
   const user_manager::User* FindUnlockUser(const AccountId& account_id);
 
+  // Callback to be invoked for ash start lock request. |locked| is true when
+  // ash is fully locked and post lock animation finishes. Otherwise, the start
+  // lock request is failed.
+  void OnStartLockCallback(bool locked);
+
   // WebUIScreenLocker instance in use.
   std::unique_ptr<WebUIScreenLocker> web_ui_;