third_party/blink/renderer/core/css/css_unset_value.h

// 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.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_UNSET_VALUE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_UNSET_VALUE_H_

#include "base/memory/scoped_refptr.h"
#include "third_party/blink/renderer/core/css/css_value.h"
#include "third_party/blink/renderer/platform/wtf/casting.h"

namespace blink {

class CSSValuePool;

namespace cssvalue {

class CORE_EXPORT CSSUnsetValue : public CSSValue {
 public:
  static CSSUnsetValue* Create();

  // Only construct through MakeGarbageCollected for the initial value. Use
  // Create() to get the pooled value.
  CSSUnsetValue() : CSSValue(kUnsetClass) {}

  String CustomCSSText() const;

  bool Equals(const CSSUnsetValue&) const { return true; }

  void TraceAfterDispatch(blink::Visitor* visitor) {
    CSSValue::TraceAfterDispatch(visitor);
  }

 private:
  friend class ::blink::CSSValuePool;
};

}  // namespace cssvalue

template <>
struct DowncastTraits<cssvalue::CSSUnsetValue> {
  static bool AllowFrom(const CSSValue& value) { return value.IsUnsetValue(); }
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_UNSET_VALUE_H_