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diff --git a/chromium/third_party/blink/renderer/core/css/css_pending_system_font_value.h b/chromium/third_party/blink/renderer/core/css/css_pending_system_font_value.h
new file mode 100644
index 00000000000..d1687283166
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+++ b/chromium/third_party/blink/renderer/core/css/css_pending_system_font_value.h
@@ -0,0 +1,67 @@
+// Copyright 2021 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_PENDING_SYSTEM_FONT_VALUE_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_PENDING_SYSTEM_FONT_VALUE_H_
+
+#include "third_party/blink/renderer/core/css/css_value.h"
+#include "third_party/blink/renderer/core/css_value_keywords.h"
+#include "third_party/blink/renderer/platform/wtf/casting.h"
+
+namespace blink {
+
+class FontSelectionValue;
+
+namespace cssvalue {
+
+// The 'font' shorthand accepts some special system font values, like 'caption'
+// (https://drafts.csswg.org/css-fonts/#valdef-font-caption).
+//
+// The resolution of these values into longhands is platform-dependent, and can
+// also depend on user's settings, like the default font size.
+//
+// The CSS parser wouldn't be able to resolve these, since we need a |Document|
+// in order to retrieve the settings, and |CSSParserContext::GetDocument()|
+// would be null when system fonts are set in UA styles.
+//
+// So the parser sets all the font longhands to a |CSSPendingSystemFontValue|,
+// and the resolution is deferred until computed-value time, when we can use
+// |StyleResolverState::GetDocument()|.
+class CSSPendingSystemFontValue : public CSSValue {
+ public:
+  static CSSPendingSystemFontValue* Create(CSSValueID);
+
+  explicit CSSPendingSystemFontValue(CSSValueID);
+
+  CSSValueID SystemFontId() const { return system_font_id_; }
+
+  const FontSelectionValue& ResolveFontStyle() const;
+  const FontSelectionValue& ResolveFontWeight() const;
+  const AtomicString& ResolveFontFamily() const;
+  float ResolveFontSize(const Document*) const;
+
+  bool Equals(const CSSPendingSystemFontValue& other) const {
+    return system_font_id_ == other.system_font_id_;
+  }
+
+  String CustomCSSText() const;
+
+  void TraceAfterDispatch(blink::Visitor*) const;
+
+ private:
+  const CSSValueID system_font_id_;
+};
+
+}  // namespace cssvalue
+
+template <>
+struct DowncastTraits<cssvalue::CSSPendingSystemFontValue> {
+  static bool AllowFrom(const CSSValue& value) {
+    return value.IsPendingSystemFontValue();
+  }
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_PENDING_SYSTEM_FONT_VALUE_H_