Pass nextTextSibling to ::before layout rebuild.

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 1280 matching lines @@
     } else if (child->isElementNode()) {
       Element* element = toElement(child);
       if (element->shouldCallRecalcStyle(change))
         element->recalcStyle(change);
       else if (element->supportsStyleSharing())
         styleResolver.addToStyleSharingList(*element);
     }
   }
 }
 
-void ContainerNode::rebuildChildrenLayoutTrees() {
+void ContainerNode::rebuildChildrenLayoutTrees(Text*& nextTextSibling) {
   DCHECK(!needsReattachLayoutTree());
 
   // 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 building the layout tree.  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
-  Text* lastTextNode = nullptr;
   for (Node* child = lastChild(); child; child = child->previousSibling()) {
     bool rebuildChild = child->needsReattachLayoutTree() ||
                         child->childNeedsReattachLayoutTree();
     if (child->isTextNode()) {
       Text* textNode = toText(child);
       if (rebuildChild)
-        textNode->rebuildTextLayoutTree(lastTextNode);
-      lastTextNode = textNode;
+        textNode->rebuildTextLayoutTree(nextTextSibling);
+      nextTextSibling = textNode;
     } else if (child->isElementNode()) {
       Element* element = toElement(child);
       if (rebuildChild)
-        element->rebuildLayoutTree(lastTextNode);
+        element->rebuildLayoutTree(nextTextSibling);
       if (element->layoutObject())
-        lastTextNode = nullptr;
+        nextTextSibling = nullptr;
     }
   }
   // 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();
 }
 
+Text* ContainerNode::findNextTextSibling() const {

[esprehn, 2017/03/28 20:56:51]

This needs a better name, it's doing something very specific that's not just
about next text siblings, it's also looking at stuff like what's in and out of
flow.

This is only used for ShadowRoot, put it in ShadowRoot.cpp as a function not a
method?

[rune, 2017/03/29 10:39:47]

PS2 adds a new method on ShadowRoot instead.

+  for (Node* sibling = firstChild(); sibling;

[esprehn, 2017/03/28 20:56:51]

This is confusing, the function says sibling, but the method is looking at kids?

[rune, 2017/03/29 10:39:47]

Acknowledged.

+       sibling = sibling->nextSibling()) {
+    if (sibling->isTextNode())
+      return toText(sibling);
+    LayoutObject* layoutObject = sibling->layoutObject();
+    if (layoutObject && !layoutObject->isFloatingOrOutOfFlowPositioned())

[esprehn, 2017/03/28 20:56:51]

Why is it safe to call this here? Wouldn't the style be out of date?

[rune, 2017/03/29 10:39:47]

This code should be executed during rebuildLayoutTree only, at which point the
distribution and style is all clean, and the shadow subtree does not need layout
tree rebuilding. See PS2 which adds a lot of DCHECKs.

+      return nullptr;
+  }
+  return nullptr;
+}
+
 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