Fix broken AttachContext from r152289

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1300 matching lines @@
     if (hasRareData()) {
         ElementRareData* data = elementRareData();
         data->setPseudoElement(BEFORE, 0);
         data->setPseudoElement(AFTER, 0);
         data->setIsInCanvasSubtree(false);
         data->resetComputedStyle();
         data->resetDynamicRestyleObservations();
     }
 
     if (ElementShadow* shadow = this->shadow()) {
-        detachChildrenIfNeeded();
+        detachChildrenIfNeeded(context);
         shadow->detach();

[esprehn, 2013/06/13 18:20:42]

You don't correctly handle ShadowRoots, you need to pass the context down
through shadow->detach and ->attach. Otherwise a :hover around a thing with a
shadow will fail the same as my test case.

     }
     ContainerNode::detach(context);
 }
 
 bool Element::pseudoStyleCacheIsInvalid(const RenderStyle* currentStyle, RenderStyle* newStyle)
 {
     ASSERT(currentStyle == renderStyle());
     ASSERT(renderer());
 
     if (!currentStyle)
@@ skipping 1787 matching lines @@
     return 0;
 }
 
 Attribute* UniqueElementData::attributeItem(unsigned index)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(index < length());
     return &m_attributeVector.at(index);
 }
 
 } // namespace WebCore