[CSS Grid Layout] Upgrade justify-content parsing to CSS3 Box Alignment spec.

Source/core/css/CSSPrimitiveValue.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
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     bool isCalculatedPercentageWithNumber() const { return primitiveType() == CSS_CALC_PERCENTAGE_WITH_NUMBER; }
     bool isCalculatedPercentageWithLength() const { return primitiveType() == CSS_CALC_PERCENTAGE_WITH_LENGTH; }
     static bool isDotsPerInch(UnitType type) { return type == CSS_DPI; }
     static bool isDotsPerPixel(UnitType type) { return type == CSS_DPPX; }
     static bool isDotsPerCentimeter(UnitType type) { return type == CSS_DPCM; }
     static bool isResolution(UnitType type) { return type >= CSS_DPPX && type <= CSS_DPCM; }
     bool isFlex() const { return primitiveType() == CSS_FR; }
     bool isValueID() const { return m_primitiveUnitType == CSS_VALUE_ID; }
     bool colorIsDerivedFromElement() const;
 
+    static bool isContentDistributionKeyword(CSSValueID id)
+    {
+        return id == CSSValueSpaceBetween || id == CSSValueSpaceAround
+            || id == CSSValueSpaceEvenly || id == CSSValueStretch;
+    }
+
+    static bool isContentPositionKeyword(CSSValueID id)
+    {
+        return id == CSSValueStart || id == CSSValueEnd || id == CSSValueCenter
+            || id == CSSValueFlexStart || id == CSSValueFlexEnd
+            || id == CSSValueLeft || id == CSSValueRight;
+    }
+
     static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createIdentifier(CSSValueID valueID)
     {
         return adoptRefWillBeNoop(new CSSPrimitiveValue(valueID));
     }
     static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createIdentifier(CSSPropertyID propertyID)
     {
         return adoptRefWillBeNoop(new CSSPrimitiveValue(propertyID));
     }
     static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createColor(unsigned rgbValue)
     {
@@ skipping 176 matching lines @@
     } m_value;
 };
 
 typedef CSSPrimitiveValue::CSSLengthArray CSSLengthArray;
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSPrimitiveValue, isPrimitiveValue());
 
 } // namespace blink
 
 #endif // CSSPrimitiveValue_h