Call Element::rebuildLayoutTree from Document::updateStyle directly

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2013 Apple 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
@@ skipping 770 matching lines @@
 
 void ContainerNode::detachLayoutTree(const AttachContext& context) {
   AttachContext childrenContext(context);
   childrenContext.resolvedStyle = nullptr;
   childrenContext.clearInvalidation = true;
 
   for (Node* child = firstChild(); child; child = child->nextSibling())
     child->detachLayoutTree(childrenContext);
 
   setChildNeedsStyleRecalc();
+  setChildNeedsReattachLayoutTree();
   Node::detachLayoutTree(context);
 }
 
 void ContainerNode::childrenChanged(const ChildrenChange& change) {
   document().incDOMTreeVersion();
   document().notifyChangeChildren(*this);
   invalidateNodeListCachesInAncestors();
   if (change.isChildInsertion() && !childNeedsStyleRecalc()) {
     setChildNeedsStyleRecalc();
     markAncestorsWithChildNeedsStyleRecalc();
+    setChildNeedsReattachLayoutTree();

[esprehn, 2017/02/16 05:49:25]

You need a separate check for !childNeedsReattach... like the
!childNeedsStyleRecalc(), otherwise if this element already had kids that needed
a style recalc you'd fail to do this work.

I think you want:

if (change.isChildInsertion()) {
  if (!childNeedsStyleRecalc()) {
    // existing two lines.
  }
  if (!childNeedsReattachLayoutTree()) {
    // new two lines.
  }
}

Should be easy to write a test for that too, ex.

element.firstElementChild.style.color = "red"; // mark a child for style recalc.

element.appendChild(anotherElement); // we wouldn't do any of the code you have
here now since it's marked.

[nainar, 2017/02/16 06:47:54]

Done. Add test in this patch or in another one?

+    markAncestorsWithChildNeedsReattachLayoutTree();
   }
 }
 
 void ContainerNode::cloneChildNodes(ContainerNode* clone) {
   DummyExceptionStateForTesting exceptionState;
   for (Node* n = firstChild(); n && !exceptionState.hadException();
        n = n->nextSibling())
     clone->appendChild(n->cloneNode(true), exceptionState);
 }
 
@@ skipping 462 matching lines @@
 }
 
 void ContainerNode::setRestyleFlag(DynamicRestyleFlags mask) {
   DCHECK(isElementNode() || isShadowRoot());
   ensureRareData().setRestyleFlag(mask);
 }
 
 void ContainerNode::recalcDescendantStyles(StyleRecalcChange change) {
   DCHECK(document().inStyleRecalc());
   DCHECK(change >= UpdatePseudoElements || childNeedsStyleRecalc());
-  DCHECK(!needsStyleRecalc());

[esprehn, 2017/02/16 05:49:25]

add this back? Recomputing the descendant styles while yourself is still dirty
is a bug.

[nainar, 2017/02/16 06:47:54]

Done. Needed to move the 

if (!needsReattachLayoutTree())
      clearNeedsStyleRecalc();

up into the scope in which we are calling recalcOwnStyle

 
   // This loop is deliberately backwards because we use insertBefore in the
   // layout tree, and want to avoid a potentially n^2 loop to find the insertion
   // point while resolving style.  Having us start from the last child and work
   // our way back means in the common case, we'll find the insertion point in
   // O(1) time.  See crbug.com/288225
   StyleResolver& styleResolver = document().ensureStyleResolver();
   Text* lastTextNode = nullptr;
   for (Node* child = lastChild(); child; child = child->previousSibling()) {
     if (child->isTextNode()) {
       toText(child)->recalcTextStyle(change, lastTextNode);
       lastTextNode = toText(child);
     } else if (child->isElementNode()) {
       Element* element = toElement(child);
       if (element->shouldCallRecalcStyle(change))
         element->recalcStyle(change, lastTextNode);
       else if (element->supportsStyleSharing())
         styleResolver.addToStyleSharingList(*element);
       if (element->layoutObject())
         lastTextNode = nullptr;
     }
   }
 }
 
+void ContainerNode::rebuildChildrenLayoutTrees() {
+  DCHECK(!needsReattachLayoutTree());
+
+  for (Node* child = lastChild(); child; child = child->previousSibling()) {
+    if (child->needsReattachLayoutTree() ||
+        child->childNeedsReattachLayoutTree()) {
+      if (child->isTextNode())
+        toText(child)->rebuildTextLayoutTree();
+      else if (child->isElementNode())
+        toElement(child)->rebuildLayoutTree();
+    }
+  }
+  clearNeedsStyleRecalc();
+  // This is done in ContainerNode::attachLayoutTree but will never be cleared
+  // if we don't enter ContainerNode::attachLayoutTree so we do it here.
+  clearChildNeedsStyleRecalc();
+  clearChildNeedsReattachLayoutTree();
+}
+
 void ContainerNode::checkForSiblingStyleChanges(SiblingCheckType changeType,
                                                 Element* changedElement,
                                                 Node* nodeBeforeChange,
                                                 Node* nodeAfterChange) {
   if (!inActiveDocument() || document().hasPendingForcedStyleRecalc() ||
       getStyleChangeType() >= SubtreeStyleChange)
     return;
 
   if (!hasRestyleFlag(ChildrenAffectedByStructuralRules))
     return;
@@ skipping 159 matching lines @@
     return true;
 
   if (node->isElementNode() && toElement(node)->shadow())
     return true;
 
   return false;
 }
 #endif
 
 }  // namespace blink