Split property priority functions out of StyleResolver.

Source/core/css/resolver/CSSPropertyPriority.h

+// Copyright 2015 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 CSSPropertyPriority_h
+#define CSSPropertyPriority_h
+
+#include "core/CSSPropertyNames.h"
+
+namespace blink {
+
+// The values of high priority properties affect the values of low priority
+// properties. For example, the value of the high priority property 'font-size'
+// decides the pixel value of low priority properties with 'em' units.
+
+enum CSSPropertyPriority {
+    HighPropertyPriority,
+    LowPropertyPriority
+};
+
+template <CSSPropertyPriority priority>
+class CSSPropertyPriorityData {
+public:
+    static inline CSSPropertyID first();
+    static inline CSSPropertyID last();
+    static inline bool propertyHasPriority(CSSPropertyID prop)
+    {
+        return first() <= prop && prop <= last();
+    }
+};
+
+template<>
+inline CSSPropertyID CSSPropertyPriorityData<HighPropertyPriority>::first()
+{
+    static_assert(CSSPropertyColor == firstCSSProperty, "CSSPropertyColor should be the first high priority property");
+    return CSSPropertyColor;
+}
+
+template<>
+inline CSSPropertyID CSSPropertyPriorityData<HighPropertyPriority>::last()
+{
+    static_assert(CSSPropertyZoom == CSSPropertyColor + 16, "CSSPropertyZoom should be the end of the high priority property range");
+    static_assert(CSSPropertyTextRendering == CSSPropertyZoom - 1, "CSSPropertyTextRendering should be immediately before CSSPropertyZoom");
+    return CSSPropertyZoom;
+}
+
+template<>
+inline CSSPropertyID CSSPropertyPriorityData<LowPropertyPriority>::first()
+{
+    static_assert(CSSPropertyAlignContent == CSSPropertyZoom + 1, "CSSPropertyAlignContent should be the first low priority property");
+    return CSSPropertyAlignContent;
+}
+
+template<>
+inline CSSPropertyID CSSPropertyPriorityData<LowPropertyPriority>::last()
+{
+    return static_cast<CSSPropertyID>(lastCSSProperty);
+}
+
+} // namespace blink
+
+#endif // CSSPropertyPriority_h