[css-ui] Add support for caret-color property

third_party/WebKit/Source/core/css/StyleAutoColor.h

+// Copyright 2016 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 StyleAutoColor_h
+#define StyleAutoColor_h
+
+#include "core/css/StyleColor.h"
+#include "platform/graphics/Color.h"
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class StyleAutoColor {
+  DISALLOW_NEW();
+
+ public:
+  StyleAutoColor(Color color)
+      : m_type(ValueType::SpecifiedColor), m_color(color) {}
+  static StyleAutoColor autoColor() { return StyleAutoColor(ValueType::Auto); }
+  static StyleAutoColor currentColor() {
+    return StyleAutoColor(ValueType::CurrentColor);
+  }
+
+  bool isAutoColor() const { return m_type == ValueType::Auto; }
+  bool isCurrentColor() const { return m_type == ValueType::CurrentColor; }
+  Color color() const {
+    DCHECK(m_type == ValueType::SpecifiedColor);
+    return m_color;
+  }
+
+  Color resolve(Color currentColor) const {
+    return m_type == ValueType::SpecifiedColor ? m_color : currentColor;
+  }
+
+  StyleColor toStyleColor() const {
+    if (m_type == ValueType::SpecifiedColor)
+      return StyleColor(m_color);
+    return StyleColor::currentColor();
+  }
+
+ private:
+  enum class ValueType { Auto, CurrentColor, SpecifiedColor };
+  StyleAutoColor(ValueType type) : m_type(type) {}
+
+  ValueType m_type;
+  Color m_color;
+};
+
+inline bool operator==(const StyleAutoColor& a, const StyleAutoColor& b) {
+  if (a.isAutoColor() || b.isAutoColor())
+    return a.isAutoColor() && b.isAutoColor();
+  if (a.isCurrentColor() || b.isCurrentColor())
+    return a.isCurrentColor() && b.isCurrentColor();
+  return a.color() == b.color();
+}
+
+inline bool operator!=(const StyleAutoColor& a, const StyleAutoColor& b) {
+  return !(a == b);
+}
+
+}  // namespace blink
+
+#endif  // StyleAutoColor_h