Have HTMLCollection::item() return an Element as per specification

Source/core/html/HTMLCollection.idl

Index: Source/core/html/HTMLCollection.idl
diff --git a/Source/core/html/HTMLCollection.idl b/Source/core/html/HTMLCollection.idl
index 2632e64de090e4a4955f3b474a716905d6abd8b6..fb9b844d1332cf0118494d229bcd3fca86106a11 100644
--- a/Source/core/html/HTMLCollection.idl
+++ b/Source/core/html/HTMLCollection.idl
@@ -24,7 +24,7 @@
     SetWrapperReferenceFrom=ownerNode,
 ] interface HTMLCollection {
     readonly attribute unsigned long length;
-    getter Node item([Default=Undefined] optional unsigned long index);
+    getter Element item([Default=Undefined] optional unsigned long index);
     Element namedItem([Default=Undefined] optional DOMString name);
     [NotEnumerable, ImplementedAs=namedItem] getter Element ([Default=Undefined] optional DOMString name);
 };