Reschedule sibling invalidations as descendant on removal.

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 4200 matching lines @@
     range->nodeWillBeRemoved(n);
 
   notifyNodeWillBeRemoved(n);
 
   if (LocalFrame* frame = this->frame()) {
     frame->selection().nodeWillBeRemoved(n);
   }
 
   if (containsV1ShadowTree())
     n.checkSlotChangeBeforeRemoved();
+
+  if (n.inActiveDocument() && n.isElementNode())
+    styleEngine().elementWillBeRemoved(toElement(n));

[esprehn, 2016/12/22 17:19:59]

Hooking here is unusual, we'd normally do Element::removed from and pass the
parent node into the thing. We should figure out how to reconcile the code here
and the code there. :/

[rune, 2016/12/23 00:06:37]

You were thinking along the lines of having a willBeRemovedFrom in Node along
insertedInto and removedFrom? And have the implementation on Element call
StyleEngine to reschedule its invalidation set?

 }
 
 void Document::dataWillChange(const CharacterData& characterData) {
   if (LocalFrame* frame = this->frame())
     frame->selection().dataWillChange(characterData);
 }
 
 void Document::didInsertText(Node* text, unsigned offset, unsigned length) {
   for (Range* range : m_ranges)
     range->didInsertText(text, offset, length);
@@ skipping 2348 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif