setAttributeNode() does not properly normalize case.

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 7b075ce8638b2e631f36a5c5516def6a933f2a61..88df55f6cedbe0b2ad9a4f0aad8401840613335c 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -87,7 +87,7 @@ public:
 
     const Attribute* attributeItem(unsigned index) const;
     const Attribute* getAttributeItem(const QualifiedName&) const;
-    size_t getAttributeItemIndex(const QualifiedName&) const;
+    size_t getAttributeItemIndex(const QualifiedName&, bool shouldIgnoreCase = false) const;
     size_t getAttributeItemIndex(const AtomicString& name, bool shouldIgnoreAttributeCase) const;
     size_t getAttrIndex(Attr*) const;
 
@@ -1037,12 +1037,12 @@ inline const Attribute* ElementData::attributeBase() const
     return static_cast<const ShareableElementData*>(this)->m_attributeArray;
 }
 
-inline size_t ElementData::getAttributeItemIndex(const QualifiedName& name) const
+inline size_t ElementData::getAttributeItemIndex(const QualifiedName& name, bool shouldIgnoreCase) const
 {
     const Attribute* begin = attributeBase();
     for (unsigned i = 0; i < length(); ++i) {
         const Attribute& attribute = begin[i];
-        if (attribute.name().matches(name))
+        if (attribute.name().matchesPossiblyIgnoringCase(name, shouldIgnoreCase))
             return i;
     }
     return notFound;