Introduce DEFINE_ELEMENT_DATA_TYPE_CASTS, and use it

Source/core/dom/ElementData.h

Index: Source/core/dom/ElementData.h
diff --git a/Source/core/dom/ElementData.h b/Source/core/dom/ElementData.h
index f7f4a07996c6b120ea9dc68fa6fa1ba45abd22b0..2eb84fb67049b0ba46438837b5a3f633ed3b94de 100644
--- a/Source/core/dom/ElementData.h
+++ b/Source/core/dom/ElementData.h
@@ -78,6 +78,7 @@ public:
     bool isEquivalent(const ElementData* other) const;
 
     bool isUnique() const { return m_isUnique; }
+    bool isShareable() const { return !m_isUnique; }
 
     void traceAfterDispatch(Visitor*);
     void trace(Visitor*);
@@ -111,6 +112,10 @@ private:
     PassRefPtrWillBeRawPtr<UniqueElementData> makeUniqueCopy() const;
 };
 
+#define DEFINE_ELEMENT_DATA_TYPE_CASTS(thisType, predicate) \
+    template<typename T> inline thisType* to##thisType(const RefPtr<T>& data) { return to##thisType(data.get()); } \

[Inactive, 2014/07/21 19:37:47]

Sorry, I thought the macro was doing this for us already. If it doesn't, it may
be on purpose (people might find it confusing that a toX() calls converts a
smart pointer into a raw one). My proposal would be to not add it.

Also, why not use DEFINE_TYPE_CASTS() directly instead of having this
intermediate macro? It would probably make introducing isShareable() useless as
we could likely use:
DEFINE_TYPE_CASTS(ShareableElementData, ElementData, data, !data->isUnique(),
!data.isUnique());

[gyuyoung-inactive, 2014/07/22 00:20:32]

I removed .get() in issue 401553002 as well. I would like to ask this to Kent
because he suggested to use it. Kent, what do you think ?
Personally I think intermediate macro is more easier to use. I would like to ask
this to Kent too.

[Inactive, 2014/07/22 00:44:29]

Ok, I see tkent's comment on the other CL, fine then. I don't really mind the
intermediate macro, especially now that we have the RefPtr helper. However, I
still think it would be nice if we did not have to introduce a isShareable()
method, just for this helper.

[tkent, 2014/07/22 00:57:12]

I agree with Chris.  Adding the intermediate macro is ok, but I feel adding
isShareable is unnecessary.

+    DEFINE_TYPE_CASTS(thisType, ElementData, data, data->predicate, data.predicate)
+
 #if COMPILER(MSVC)
 #pragma warning(push)
 #pragma warning(disable: 4200) // Disable "zero-sized array in struct/union" warning
@@ -145,6 +150,8 @@ public:
     Attribute m_attributeArray[0];
 };
 
+DEFINE_ELEMENT_DATA_TYPE_CASTS(ShareableElementData, isShareable());
+
 #if COMPILER(MSVC)
 #pragma warning(pop)
 #endif
@@ -183,6 +190,8 @@ public:
     Vector<Attribute, 4> m_attributeVector;
 };
 
+DEFINE_ELEMENT_DATA_TYPE_CASTS(UniqueElementData, isUnique());
+
 #if !ENABLE(OILPAN)
 inline void ElementData::deref()
 {
@@ -196,14 +205,14 @@ 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