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

Source/core/rendering/RenderFlexibleBox.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1310 matching lines @@
                 // FIXME: If we get here in columns, we want the use the descent, except we currently can't get the ascent/descent of orthogonal children.
                 // https://bugs.webkit.org/show_bug.cgi?id=98076
                 LayoutUnit ascent = marginBoxAscentForChild(child);
                 LayoutUnit startOffset = maxAscent - ascent;
                 adjustAlignmentForChild(child, startOffset);
 
                 if (style()->flexWrap() == FlexWrapReverse)
                     minMarginAfterBaseline = std::min(minMarginAfterBaseline, availableAlignmentSpaceForChild(lineCrossAxisExtent, child) - startOffset);
                 break;
             }
+            case ItemPositionLastBaseline:
             case ItemPositionSelfStart:
             case ItemPositionSelfEnd:
             case ItemPositionStart:
             case ItemPositionEnd:
             case ItemPositionLeft:
             case ItemPositionRight:
                 // FIXME: File a bug about implementing that. The extended grammar
                 // is not enabled by default so we shouldn't hit this codepath.
                 ASSERT_NOT_REACHED();
                 break;
@@ skipping 75 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(child, newOffset - originalOffset);
         }
     }
 }
 
 }