cros: Implement cryptohome backend for pin.

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 dba07eb44bdd26fa11b408c417e09a9f89f03d63..51a057d42c0a4ce1f595ac374df205358a76fcc5 100644
--- a/chrome/browser/chromeos/login/lock/screen_locker.h
+++ b/chrome/browser/chromeos/login/lock/screen_locker.h
@@ -228,6 +228,13 @@ class ScreenLocker : public AuthStatusConsumer,
   // lock request is failed.
   void OnStartLockCallback(bool locked);
 
+  // Called when the pin attempt is finished running.
+  void OnPinAttemptDone(const UserContext& user_context, bool success);
+
+  // Called to continue authentication against cryptohome after the pin login
+  // check has completed.
+  void ContinueAuthenticate(const UserContext& user_context);
+
   // WebUIScreenLocker instance in use.
   std::unique_ptr<WebUIScreenLocker> web_ui_;