Added CSSPropertyPositionUtils which holds position parsing methods.

third_party/WebKit/Source/core/css/properties/CSSPropertyPositionUtils.h

+// Copyright 2017 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 CSSPropertyPositionUtils_h
+#define CSSPropertyPositionUtils_h
+
+#include "core/CSSValueKeywords.h"
+#include "core/css/parser/CSSParserMode.h"
+
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class CSSParserTokenRange;
+class CSSValue;
+
+class CSSPropertyPositionUtils {
+  STATIC_ONLY(CSSPropertyPositionUtils);
+
+  template <CSSValueID start, CSSValueID end>
+  static CSSValue* consumePositionLonghand(CSSParserTokenRange& range,
+                                           CSSParserMode cssParserMode) {
+    if (range.peek().type() == IdentToken) {
+      CSSValueID id = range.peek().id();
+      int percent;
+      if (id == start)
+        percent = 0;
+      else if (id == CSSValueCenter)
+        percent = 50;
+      else if (id == end)
+        percent = 100;
+      else
+        return nullptr;
+      range.consumeIncludingWhitespace();
+      return CSSPrimitiveValue::create(percent,
+                                       CSSPrimitiveValue::UnitType::Percentage);
+    }
+    return CSSPropertyParserHelpers::consumeLengthOrPercent(
+        range, cssParserMode, ValueRangeAll);
+  }
+};
+
+}  // namespace blink
+
+#endif  // CSSPropertyPositionUtils_h