Have Element::ensureUniqueElementData() return a reference

Source/core/html/HTMLSelectElement.cpp

Index: Source/core/html/HTMLSelectElement.cpp
diff --git a/Source/core/html/HTMLSelectElement.cpp b/Source/core/html/HTMLSelectElement.cpp
index 56a6c45a59e7f11cf12d1a609dd95a013b9ea7bb..710aff5591e54959d330111276ae8f5207eb4bde 100644
--- a/Source/core/html/HTMLSelectElement.cpp
+++ b/Source/core/html/HTMLSelectElement.cpp
@@ -274,7 +274,7 @@ void HTMLSelectElement::parseAttribute(const QualifiedName& name, const AtomicSt
         AtomicString attrSize = AtomicString::number(size);
         if (attrSize != value) {
             // FIXME: This is horribly factored.
-            if (Attribute* sizeAttribute = ensureUniqueElementData()->getAttributeItem(sizeAttr))
+            if (Attribute* sizeAttribute = ensureUniqueElementData().getAttributeItem(sizeAttr))
                 sizeAttribute->setValue(attrSize);
         }
         size = max(size, 1);