[CSS Grid Layout] Implement 'justify-items' parsing

Source/core/rendering/style/StyleRareNonInheritedData.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
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     unsigned m_hasAspectRatio : 1; // Whether or not an aspect ratio has been specified.
 
     unsigned m_effectiveBlendMode: 5; // EBlendMode
 
     unsigned m_touchAction : TouchActionBits; // TouchAction
 
     unsigned m_objectFit : 3; // ObjectFit
 
     unsigned m_isolation : 1; // Isolation
 
+    unsigned m_justifyItems : 4; // ItemPosition
+    unsigned m_justifyItemsOverflowAlignment : 2; // OverflowAlignment
+    unsigned m_justifyItemsPositionType: 1; // Whether or not alignment uses the 'legacy' keyword.
+
     unsigned m_justifySelf : 4; // ItemPosition
     unsigned m_justifySelfOverflowAlignment : 2; // OverflowAlignment
 
     // ScrollBehavior. 'scroll-behavior' has 2 accepted values, but ScrollBehavior has a third
     // value (that can only be specified using CSSOM scroll APIs) so 2 bits are needed.
     unsigned m_scrollBehavior: 2;
 
     // Plugins require accelerated compositing for reasons external to blink.
     // In which case, we need to update the RenderStyle on the RenderEmbeddedObject,
     // so store this bit so that the style actually changes when the plugin
     // becomes composited.
     unsigned m_requiresAcceleratedCompositingForExternalReasons: 1;
 
 private:
     StyleRareNonInheritedData();
     StyleRareNonInheritedData(const StyleRareNonInheritedData&);
 };
 
 } // namespace WebCore
 
 #endif // StyleRareNonInheritedData_h