Implement the ::backdrop pseudo-element for modal <dialog>.

Source/core/dom/ElementRareData.h

 /*
  * Copyright (C) 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 David Smith <catfish.man@gmail.com>
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 168 matching lines @@
     OwnPtr<DatasetDOMStringMap> m_dataset;
     OwnPtr<ClassList> m_classList;
     OwnPtr<ElementShadow> m_shadow;
     OwnPtr<NamedNodeMap> m_attributeMap;
     OwnPtr<InputMethodContext> m_inputMethodContext;
 
     OwnPtr<Vector<Animation*> > m_activeAnimations;
 
     RefPtr<PseudoElement> m_generatedBefore;
     RefPtr<PseudoElement> m_generatedAfter;
+    RefPtr<PseudoElement> m_backdrop;
 
     ElementRareData(RenderObject*);
     void releasePseudoElement(PseudoElement*);
 };
 
 inline IntSize defaultMinimumSizeForResizing()
 {
     return IntSize(LayoutUnit::max(), LayoutUnit::max());
 }
 
@@ skipping 20 matching lines @@
     , m_regionOversetState(RegionUndefined)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
 {
 }
 
 inline ElementRareData::~ElementRareData()
 {
     ASSERT(!m_shadow);
     ASSERT(!m_generatedBefore);
     ASSERT(!m_generatedAfter);
+    ASSERT(!m_backdrop);
 }
 
 inline void ElementRareData::setPseudoElement(PseudoId pseudoId, PassRefPtr<PseudoElement> element)
 {
     switch (pseudoId) {
     case BEFORE:
         releasePseudoElement(m_generatedBefore.get());
         m_generatedBefore = element;
         break;
     case AFTER:
         releasePseudoElement(m_generatedAfter.get());
         m_generatedAfter = element;
         break;
+    case BACKDROP:
+        releasePseudoElement(m_backdrop.get());
+        m_backdrop = element;
+        break;
     default:
         ASSERT_NOT_REACHED();
     }
 }
 
 inline PseudoElement* ElementRareData::pseudoElement(PseudoId pseudoId) const
 {
     switch (pseudoId) {
     case BEFORE:
         return m_generatedBefore.get();
     case AFTER:
         return m_generatedAfter.get();
+    case BACKDROP:
+        return m_backdrop.get();
     default:
         return 0;
     }
 }
 
 inline void ElementRareData::releasePseudoElement(PseudoElement* element)
 {
     if (!element)
         return;
 
     if (element->attached())
         element->detach();
 
     ASSERT(!element->nextSibling());
     ASSERT(!element->previousSibling());
 
+    element->document()->removeFromTopLayer(element);
     element->setParentOrShadowHostNode(0);
 }
 
 inline void ElementRareData::resetComputedStyle()
 {
     setComputedStyle(0);
     setStyleAffectedByEmpty(false);
     setChildIndex(0);
 }
 
 inline void ElementRareData::resetDynamicRestyleObservations()
 {
     setChildrenAffectedByHover(false);
     setChildrenAffectedByActive(false);
     setChildrenAffectedByDrag(false);
     setChildrenAffectedByFirstChildRules(false);
     setChildrenAffectedByLastChildRules(false);
     setChildrenAffectedByDirectAdjacentRules(false);
     setChildrenAffectedByForwardPositionalRules(false);
     setChildrenAffectedByBackwardPositionalRules(false);
 }
 
 } // namespace
 
 #endif // ElementRareData_h