[Sync] Replacing NULL with nullptr/null throughout sync code.

chrome/browser/sync/sync_error_notifier_ash_unittest.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 "chrome/browser/sync/sync_error_notifier_ash.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 36 matching lines @@
 
 namespace {
 
 const char kTestAccountId[] = "testuser@test.com";
 
 // Notification ID corresponding to kProfileSyncNotificationId + kTestAccountId.
 const char kNotificationId[] = "chrome://settings/sync/testuser@test.com";
 
 class FakeLoginUIService: public LoginUIService {
  public:
-  FakeLoginUIService() : LoginUIService(NULL) {}
+  FakeLoginUIService() : LoginUIService(nullptr) {}
   ~FakeLoginUIService() override {}
 };
 
 class FakeLoginUI : public LoginUIService::LoginUI {
  public:
   FakeLoginUI() : focus_ui_call_count_(0) {}
 
   ~FakeLoginUI() override {}
 
   int focus_ui_call_count() const { return focus_ui_call_count_; }
@@ skipping 160 matching lines @@
     SCOPED_TRACE("Not expecting notification since sync setup is incomplete");
     VerifySyncErrorNotifierResult(
         GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS,
         false /* not signed in */,
         false /* no error */);
   }
 }
 
 }  // namespace test
 }  // namespace ash