Introduce DEFINE_ELEMENT_DATA_TYPE_CASTS, and use it

Source/core/dom/ElementData.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 2014 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 93 matching lines @@
     friend class UniqueElementData;
     friend class SVGElement;
 
 #if !ENABLE(OILPAN)
     void destroy();
 #endif
 
     PassRefPtrWillBeRawPtr<UniqueElementData> makeUniqueCopy() const;
 };
 
+#define DEFINE_ELEMENT_DATA_TYPE_CASTS(thisType, predicate) \
+    DEFINE_TYPE_CASTS(thisType, ElementData, data, data->isUnique() == predicate, data.isUnique() == predicate)
+
 #if COMPILER(MSVC)
 #pragma warning(push)
 #pragma warning(disable: 4200) // Disable "zero-sized array in struct/union" warning
 #endif
 
 // SharableElementData is managed by ElementDataCache and is produced by
 // the parser during page load for elements that have identical attributes. This
 // is a memory optimization since it's very common for many elements to have
 // duplicate sets of attributes (ex. the same classes).
 class ShareableElementData FINAL : public ElementData {
@@ skipping 14 matching lines @@
     void* operator new(std::size_t, void* location)
     {
         return location;
     }
 
     AttributeCollection attributes() const;
 
     Attribute m_attributeArray[0];
 };
 
+DEFINE_ELEMENT_DATA_TYPE_CASTS(ShareableElementData, false);

[Inactive, 2014/07/21 12:14:00]

nit: I would have introduced a "isShareable()" method and used it here. I find
it not very readable to have a boolean macro parameter here.

+
 #if COMPILER(MSVC)
 #pragma warning(pop)
 #endif
 
 // UniqueElementData is created when an element needs to mutate its attributes
 // or gains presentation attribute style (ex. width="10"). It does not need to
 // be created to fill in values in the ElementData that are derived from
 // attributes. For example populating the m_inlineStyle from the style attribute
 // doesn't require a UniqueElementData as all elements with the same style
 // attribute will have the same inline style.
@@ skipping 18 matching lines @@
     void traceAfterDispatch(Visitor*);
 
     // FIXME: We might want to support sharing element data for elements with
     // presentation attribute style. Lots of table cells likely have the same
     // attributes. Most modern pages don't use presentation attributes though
     // so this might not make sense.
     mutable RefPtrWillBeMember<StylePropertySet> m_presentationAttributeStyle;
     Vector<Attribute, 4> m_attributeVector;
 };
 
+DEFINE_ELEMENT_DATA_TYPE_CASTS(UniqueElementData, true);

[Inactive, 2014/07/21 12:14:00]

ditto: s/true/isUnique

+
 #if !ENABLE(OILPAN)
 inline void ElementData::deref()
 {
     if (!derefBase())
         return;
     destroy();
 }
 #endif
 
 inline const StylePropertySet* ElementData::presentationAttributeStyle() const
 {
     if (!m_isUnique)
         return 0;
-    return static_cast<const UniqueElementData*>(this)->m_presentationAttributeStyle.get();
+    return toUniqueElementData(this)->m_presentationAttributeStyle.get();
 }
 
 inline AttributeCollection ElementData::attributes() const
 {
     if (isUnique())
-        return static_cast<const UniqueElementData*>(this)->attributes();
-    return static_cast<const ShareableElementData*>(this)->attributes();
+        return toUniqueElementData(this)->attributes();
+    return toShareableElementData(this)->attributes();
 }
 
 inline AttributeCollection ShareableElementData::attributes() const
 {
     return AttributeCollection(m_attributeArray, m_arraySize);
 }
 
 inline AttributeCollection UniqueElementData::attributes() const
 {
     return AttributeCollection(m_attributeVector.data(), m_attributeVector.size());
@@ skipping 10 matching lines @@
 }
 
 inline Attribute& UniqueElementData::attributeAt(unsigned index)
 {
     return m_attributeVector.at(index);
 }
 
 } // namespace blink
 
 #endif // ElementData_h