[css-align] Avoid the style Reattach whenever align-items changes.

third_party/WebKit/Source/core/layout/LayoutGrid.cpp

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1887 matching lines @@
     case GridAxisCenter: {
         size_t childEndLine = rowsSpan.resolvedFinalPosition();
         LayoutUnit endOfRow = m_rowPositions[childEndLine];
         // m_rowPositions include gutters so we need to subtract them to get the actual end position for a given
         // row (this does not have to be done for the last track as there are no more m_rowPositions after it)
         if (childEndLine < m_rowPositions.size() - 1)
             endOfRow -= guttersSize(ForRows, 2);
         LayoutUnit childBreadth = child.logicalHeight() + child.marginLogicalHeight();
         if (childEndLine - childStartLine > 1 && childEndLine < m_rowPositions.size() - 1)
             endOfRow -= offsetBetweenTracks(styleRef().alignContentDistribution(), m_rowPositions, childBreadth);
-        LayoutUnit offsetFromStartPosition = computeOverflowAlignmentOffset(child.styleRef().alignSelfOverflowAlignment(), endOfRow - startOfRow, childBreadth);
+        OverflowAlignment overflow = ComputedStyle::resolvedAlignment(styleRef(), child.styleRef(), ItemPositionStretch).overflow();

[esprehn, 2016/01/29 04:20:55]

this should be an instance method.

styleRef().resolveAlignment(child.styleRef(), ItemPositionStretch).overflow()

+        LayoutUnit offsetFromStartPosition = computeOverflowAlignmentOffset(overflow, endOfRow - startOfRow, childBreadth);
         return startPosition + (axisPosition == GridAxisEnd ? offsetFromStartPosition : offsetFromStartPosition / 2);
     }
     }
 
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 LayoutUnit LayoutGrid::rowAxisOffsetForChild(const LayoutBox& child) const
 {
@@ skipping 153 matching lines @@
 
     return LayoutPoint(rowAxisOffset, columnAxisOffsetForChild(child));
 }
 
 void LayoutGrid::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
 {
     GridPainter(*this).paintChildren(paintInfo, paintOffset);
 }
 
 } // namespace blink