Introduce DEFINE_ELEMENT_DATA_TYPE_CASTS, and use it

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 3099 matching lines @@
     // if the idForStyleResolution and the className need different casing.
     bool ownerDocumentsHaveDifferentCaseSensitivity = false;
     if (other.hasClass() || other.hasID())
         ownerDocumentsHaveDifferentCaseSensitivity = other.document().inQuirksMode() != document().inQuirksMode();
 
     // If 'other' has a mutable ElementData, convert it to an immutable one so we can share it between both elements.
     // We can only do this if there are no presentation attributes and sharing the data won't result in different case sensitivity of class or id.
     if (other.m_elementData->isUnique()
         && !ownerDocumentsHaveDifferentCaseSensitivity
         && !other.m_elementData->presentationAttributeStyle())
-        const_cast<Element&>(other).m_elementData = static_cast<const UniqueElementData*>(other.m_elementData.get())->makeShareableCopy();
+        const_cast<Element&>(other).m_elementData = toUniqueElementData(other.m_elementData)->makeShareableCopy();
 
     if (!other.m_elementData->isUnique() && !ownerDocumentsHaveDifferentCaseSensitivity && !needsURLResolutionForInlineStyle(other, other.document(), document()))
         m_elementData = other.m_elementData;
     else
         m_elementData = other.m_elementData->makeUniqueCopy();
 
     AttributeCollection attributes = m_elementData->attributes();
     AttributeCollection::const_iterator end = attributes.end();
     for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it)
         attributeChangedFromParserOrByCloning(it->name(), it->value(), ModifiedByCloning);
 }
 
 void Element::cloneDataFromElement(const Element& other)
 {
     cloneAttributesFromElement(other);
     copyNonAttributePropertiesFromElement(other);
 }
 
 void Element::createUniqueElementData()
 {
     if (!m_elementData)
         m_elementData = UniqueElementData::create();
     else {
         ASSERT(!m_elementData->isUnique());
-        m_elementData = static_cast<ShareableElementData*>(m_elementData.get())->makeUniqueCopy();
+        m_elementData = toShareableElementData(m_elementData)->makeUniqueCopy();
     }
 }
 
 InputMethodContext& Element::inputMethodContext()
 {
     return ensureElementRareData().ensureInputMethodContext(toHTMLElement(this));
 }
 
 bool Element::hasInputMethodContext() const
 {
@@ skipping 211 matching lines @@
 {
 #if ENABLE(OILPAN)
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
 #endif
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink