[Password Manager Cleanup] Replaces NULL -> nullptr.

chrome/browser/password_manager/mock_password_store_service.cc

Index: chrome/browser/password_manager/mock_password_store_service.cc
diff --git a/chrome/browser/password_manager/mock_password_store_service.cc b/chrome/browser/password_manager/mock_password_store_service.cc
index b2e9b786d230b2a2f93985c1f6e7eb9b4e3e1edf..f3acb90de835ffbd50e164cdb4cf60364a65d24e 100644
--- a/chrome/browser/password_manager/mock_password_store_service.cc
+++ b/chrome/browser/password_manager/mock_password_store_service.cc
@@ -12,7 +12,7 @@ KeyedService* MockPasswordStoreService::Build(
   scoped_refptr<password_manager::PasswordStore> store(
       new password_manager::MockPasswordStore);
   if (!store.get() || !store->Init(syncer::SyncableService::StartSyncFlare()))
-    return NULL;
+    return nullptr;
   return new MockPasswordStoreService(store);
 }