Begin tracking why layout is invalidated

Source/core/layout/LayoutBlockFlowLine.cpp

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * 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 1681 matching lines @@
                 break;
         }
         // Check if a new float has been inserted after the last known float.
         if (!curr && floatIndex < layoutState.floats().size())
             layoutState.markForFullLayout();
     }
 
     if (layoutState.isFullLayout()) {
         // If we encountered a new float and have inline children, mark ourself to force us to issue paint invalidations.
         if (layoutState.hasInlineChild() && !selfNeedsLayout()) {
-            setNeedsLayoutAndFullPaintInvalidation(MarkOnlyThis);
+            setNeedsLayoutAndFullPaintInvalidation(LayoutInvalidationReason::FloatDescendantChanged, MarkOnlyThis);
             setShouldDoFullPaintInvalidation();
         }
 
         // FIXME: This should just call deleteLineBoxTree, but that causes
         // crashes for fast/repaint tests.
         curr = firstRootBox();
         while (curr) {
             // Note: This uses nextRootBox() insted of nextLineBox() like deleteLineBoxTree does.
             RootInlineBox* next = curr->nextRootBox();
             curr->deleteLine();
@@ skipping 343 matching lines @@
     float logicalLeft = logicalLeftOffsetForLine(logicalHeight(), false).toFloat();
     float availableLogicalWidth = logicalRightOffsetForLine(logicalHeight(), false) - logicalLeft;
     updateLogicalWidthForAlignment(textAlign, 0, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
 
     if (!style()->isLeftToRightDirection())
         return logicalWidth() - logicalLeft;
     return logicalLeft;
 }
 
 }