Begin tracking why layout is invalidated

Source/core/layout/LayoutObjectChildList.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. 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
@@ skipping 47 matching lines @@
     ASSERT(this == owner->virtualChildren());
 
     if (oldChild->isFloatingOrOutOfFlowPositioned())
         toLayoutBox(oldChild)->removeFloatingOrPositionedChildFromBlockLists();
 
     {
         // So that we'll get the appropriate dirty bit set (either that a normal flow child got yanked or
         // that a positioned child got yanked). We also issue paint invalidations, so that the area exposed when the child
         // disappears gets paint invalidated properly.
         if (!owner->documentBeingDestroyed() && notifyRenderer && oldChild->everHadLayout()) {
-            oldChild->setNeedsLayoutAndPrefWidthsRecalc();
+            oldChild->setNeedsLayoutAndPrefWidthsRecalc(LayoutInvalidationReason::RemovedFromLayout);
             invalidatePaintOnRemoval(*oldChild);
         }
     }
 
     // If we have a line box wrapper, delete it.
     if (oldChild->isBox())
         toLayoutBox(oldChild)->deleteLineBoxWrapper();
 
     // If oldChild is the start or end of the selection, then clear the selection to
     // avoid problems of invalid pointers.
@@ skipping 70 matching lines @@
         setLastChild(newChild);
     }
 
     if (!owner->documentBeingDestroyed() && notifyRenderer)
         newChild->insertedIntoTree();
 
     if (!owner->documentBeingDestroyed()) {
         LayoutCounter::rendererSubtreeAttached(newChild);
     }
 
-    newChild->setNeedsLayoutAndPrefWidthsRecalc();
+    newChild->setNeedsLayoutAndPrefWidthsRecalc(LayoutInvalidationReason::AddedToLayout);
     newChild->setShouldDoFullPaintInvalidation(PaintInvalidationRendererInsertion);
     if (!owner->normalChildNeedsLayout())
         owner->setChildNeedsLayout(); // We may supply the static position for an absolute positioned child.
 
     if (AXObjectCache* cache = owner->document().axObjectCache())
         cache->childrenChanged(owner);
 }
 
 void LayoutObjectChildList::invalidatePaintOnRemoval(const LayoutObject& oldChild)
 {
     if (!oldChild.isRooted())
         return;
     if (oldChild.isBody()) {
         oldChild.view()->setShouldDoFullPaintInvalidation();
         return;
     }
 
     DisableCompositingQueryAsserts disabler;
     // FIXME: We should not allow paint invalidation out of paint invalidation state. crbug.com/457415
     DisablePaintInvalidationStateAsserts paintInvalidationAssertDisabler;
     const LayoutBoxModelObject* paintInvalidationContainer = oldChild.containerForPaintInvalidation();
     oldChild.invalidatePaintUsingContainer(paintInvalidationContainer, oldChild.previousPaintInvalidationRect(), PaintInvalidationRendererRemoval);
     if (RuntimeEnabledFeatures::slimmingPaintEnabled())
         oldChild.invalidateDisplayItemClients(*paintInvalidationContainer);
 }
 
 } // namespace blink