UMA for pin unlock success/failure.

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

 // Copyright (c) 2013 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.
 
 #include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <vector>
@@ skipping 1041 matching lines @@
   return !ScreenLocker::default_screen_locker() &&
          is_account_picker_showing_first_time_;
 }
 
 void SigninScreenHandler::UpdateAddButtonStatus() {
   CallJS("cr.ui.login.DisplayManager.updateAddUserButtonStatus",
          AllWhitelistedUsersPresent());
 }
 
 void SigninScreenHandler::HandleAuthenticateUser(const AccountId& account_id,
-                                                 const std::string& password) {
+                                                 const std::string& password,
+                                                 bool authenticated_by_pin) {
   if (!delegate_)
     return;
   DCHECK_EQ(account_id.GetUserEmail(),
             gaia::SanitizeEmail(account_id.GetUserEmail()));
+  chromeos::PinStorage* pin_storage =
+    chromeos::PinStorageFactory::GetForAccountId(account_id);
+  DCHECK(pin_storage);
+  DCHECK(authenticated_by_pin == pin_storage->IsPinAuthenticationAvailable());

[jdufault, 2016/08/16 17:55:02]

Will authenticated_by_pin be true if the user types their password using the
virtual keyboard when the PIN keyboard is not shown?

If not, we should change this to

  DCHECK(pin_storage->IsPinAuthenticationAvailable() || !authenticated_by_pin)

Ie, if pin storage is not available, authenticated by PIN must be false. I'd add
a comment as well since that DCHECK is non-trivial to read.

Sorry for so many iterations here.

[sammiequon, 2016/08/16 19:22:11]

Done. Authenticated by pin will be true if the pin-keyboard was visible.

 
   UserContext user_context(account_id);
   user_context.SetKey(Key(password));
+  user_context.SetIsUsingPin(authenticated_by_pin);
   delegate_->Login(user_context, SigninSpecifics());
 
   HidePinKeyboardIfNeeded(account_id);
 }
 
 void SigninScreenHandler::HandleLaunchIncognito() {
   UserContext context(user_manager::USER_TYPE_GUEST, EmptyAccountId());
   if (delegate_)
     delegate_->Login(context, SigninSpecifics());
 }
@@ skipping 414 matching lines @@
 }
 
 void SigninScreenHandler::OnFeedbackFinished() {
   CallJS("login.UnrecoverableCryptohomeErrorScreen.resumeAfterFeedbackUI");
 
   // Recreate user's cryptohome after the feedback is attempted.
   HandleResyncUserData();
 }
 
 }  // namespace chromeos