Support the essential part of Shadow DOM v1

third_party/WebKit/Source/core/dom/LayoutTreeBuilder.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, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 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
@@ skipping 30 matching lines @@
 #include "core/layout/LayoutView.h"
 #include "core/svg/SVGElement.h"
 #include "platform/RuntimeEnabledFeatures.h"
 
 namespace blink {
 
 LayoutTreeBuilderForElement::LayoutTreeBuilderForElement(Element& element, ComputedStyle* style)
     : LayoutTreeBuilder(element, nullptr)
     , m_style(style)
 {
-    ASSERT(!isActiveInsertionPoint(element));
+    ASSERT(!element.isSlotOrActiveInsertionPoint());
     if (element.isFirstLetterPseudoElement()) {
         if (LayoutObject* nextLayoutObject = FirstLetterPseudoElement::firstLetterTextLayoutObject(element))
             m_layoutObjectParent = nextLayoutObject->parent();
     } else if (ContainerNode* containerNode = LayoutTreeBuilderTraversal::parent(element)) {
         m_layoutObjectParent = containerNode->layoutObject();
     }
 }
 
 LayoutObject* LayoutTreeBuilderForElement::nextLayoutObject() const
 {
@@ skipping 101 matching lines @@
     newLayoutObject->setIsInsideFlowThread(m_layoutObjectParent->isInsideFlowThread());
 
     LayoutObject* nextLayoutObject = this->nextLayoutObject();
     m_node->setLayoutObject(newLayoutObject);
     // Parent takes care of the animations, no need to call setAnimatableStyle.
     newLayoutObject->setStyle(&style);
     m_layoutObjectParent->addChild(newLayoutObject, nextLayoutObject);
 }
 
 }