Begin tracking why layout is invalidated

Source/core/layout/LayoutFieldset.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.
  *
  * 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.
@@ skipping 49 matching lines @@
 
         m_minPreferredLogicalWidth = max(m_minPreferredLogicalWidth, legendMinWidth + borderAndPaddingWidth());
     }
 }
 
 LayoutObject* LayoutFieldset::layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope&)
 {
     LayoutBox* legend = findLegend();
     if (legend) {
         if (relayoutChildren)
-            legend->setNeedsLayoutAndFullPaintInvalidation();
+            legend->setNeedsLayoutAndFullPaintInvalidation(LayoutInvalidationReason::FieldsetChanged);
         legend->layoutIfNeeded();
 
         LayoutUnit logicalLeft;
         if (style()->isLeftToRightDirection()) {
             switch (legend->style()->textAlign()) {
             case CENTER:
                 logicalLeft = (logicalWidth() - logicalWidthForChild(*legend)) / 2;
                 break;
             case RIGHT:
                 logicalLeft = logicalWidth() - borderEnd() - paddingEnd() - logicalWidthForChild(*legend);
@@ skipping 61 matching lines @@
 {
     FieldsetPainter(*this).paintBoxDecorationBackground(paintInfo, paintOffset);
 }
 
 void LayoutFieldset::paintMask(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     FieldsetPainter(*this).paintMask(paintInfo, paintOffset);
 }
 
 } // namespace blink