Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

third_party/WebKit/Source/core/style/DataRef.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef DataRef_h
 #define DataRef_h
 
-#include "platform/heap/Handle.h"
 #include "wtf/Allocator.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 template <typename T> class DataRef {
     USING_FAST_MALLOC(DataRef);
 public:
     const T* get() const { return m_data.get(); }
 
@@ skipping 28 matching lines @@
     }
 
     void operator=(std::nullptr_t) { m_data = nullptr; }
 private:
     RefPtr<T> m_data;
 };
 
 } // namespace blink
 
 #endif // DataRef_h