[Password Manager Cleanup] Replaces NULL -> nullptr.

components/password_manager/core/browser/stub_password_manager_driver.cc

 // 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.
 
 #include "components/password_manager/core/browser/stub_password_manager_driver.h"
 
 namespace password_manager {
 
 StubPasswordManagerDriver::StubPasswordManagerDriver() {
 }
@@ skipping 24 matching lines @@
 void StubPasswordManagerDriver::PreviewSuggestion(
     const base::string16& username,
     const base::string16& password) {
 }
 
 void StubPasswordManagerDriver::ClearPreviewedForm() {
 }
 
 PasswordGenerationManager*
 StubPasswordManagerDriver::GetPasswordGenerationManager() {
-  return NULL;
+  return nullptr;
 }
 
 PasswordManager* StubPasswordManagerDriver::GetPasswordManager() {
-  return NULL;
+  return nullptr;
 }
 
 PasswordAutofillManager*
 StubPasswordManagerDriver::GetPasswordAutofillManager() {
-  return NULL;
+  return nullptr;
 }
 
 }  // namespace password_manager