[SyncFS] Use nullptr instead of NULL

chrome/browser/sync_file_system/local/syncable_file_system_unittest.cc

 // Copyright 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 "base/stl_util.h"
 #include "base/thread_task_runner_handle.h"
 #include "chrome/browser/sync_file_system/local/canned_syncable_file_system.h"
 #include "chrome/browser/sync_file_system/local/local_file_change_tracker.h"
 #include "chrome/browser/sync_file_system/local/local_file_sync_context.h"
 #include "chrome/browser/sync_file_system/local/sync_file_system_backend.h"
@@ skipping 41 matching lines @@
                                  base::ThreadTaskRunnerHandle::Get().get(),
                                  base::ThreadTaskRunnerHandle::Get().get());
     ASSERT_EQ(
         sync_file_system::SYNC_STATUS_OK,
         file_system_.MaybeInitializeFileSystemContext(sync_context_.get()));
   }
 
   virtual void TearDown() {
     if (sync_context_.get())
       sync_context_->ShutdownOnUIThread();
-    sync_context_ = NULL;
+    sync_context_ = nullptr;
 
     file_system_.TearDown();
 
     // Make sure we don't leave the external filesystem.
     // (CannedSyncableFileSystem::TearDown does not do this as there may be
     // multiple syncable file systems registered for the name)
     RevokeSyncableFileSystem();
   }
 
  protected:
@@ skipping 169 matching lines @@
                                   sync_file_system::SYNC_FILE_TYPE_DIRECTORY));
   VerifyAndClearChange(URL(kPath1),
                        FileChange(FileChange::FILE_CHANGE_DELETE,
                                   sync_file_system::SYNC_FILE_TYPE_DIRECTORY));
   VerifyAndClearChange(URL(kPath2),
                        FileChange(FileChange::FILE_CHANGE_DELETE,
                                   sync_file_system::SYNC_FILE_TYPE_FILE));
 }
 
 }  // namespace sync_file_system