Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/modules/filesystem/SyncCallbackHelper.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 152 matching lines @@
     }
 
     ResultStorageType m_result;
     FileError::ErrorCode m_errorCode;
     bool m_completed;
 };
 
 struct EmptyType : public RefCounted<EmptyType> {
     static PassRefPtr<EmptyType> create(EmptyType*)
     {
-        return 0;
+        return nullptr;
     }
 };
 
 typedef SyncCallbackHelper<EntryCallback, Entry*, EntrySync> EntrySyncCallbackHelper;
 typedef SyncCallbackHelper<EntriesCallback, const EntryVector&, EntrySyncVector> EntriesSyncCallbackHelper;
 typedef SyncCallbackHelper<MetadataCallback, Metadata*, Metadata> MetadataSyncCallbackHelper;
 typedef SyncCallbackHelper<VoidCallback, EmptyType*, EmptyType> VoidSyncCallbackHelper;
 typedef SyncCallbackHelper<FileSystemCallback, DOMFileSystem*, DOMFileSystemSync> FileSystemSyncCallbackHelper;
 
 } // namespace WebCore
 
 #endif // SyncCallbackHelper_h