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

Source/core/html/forms/RangeInputType.cpp

Index: Source/core/html/forms/RangeInputType.cpp
diff --git a/Source/core/html/forms/RangeInputType.cpp b/Source/core/html/forms/RangeInputType.cpp
index ff9fbad899899c13523e0fc9bfa0b02610357e43..55a99154277ea6febb63f2cbbadd3ca24d2fd5f0 100644
--- a/Source/core/html/forms/RangeInputType.cpp
+++ b/Source/core/html/forms/RangeInputType.cpp
@@ -356,10 +356,10 @@ void RangeInputType::updateTickMarkValues()
     RefPtr<HTMLCollection> options = dataList->options();
     m_tickMarkValues.reserveCapacity(options->length());
     for (unsigned i = 0; i < options->length(); ++i) {
-        Node* node = options->item(i);
-        HTMLOptionElement* optionElement = toHTMLOptionElement(node);
+        Element* element = options->item(i);
+        HTMLOptionElement* optionElement = toHTMLOptionElement(element);
         String optionValue = optionElement->value();
-        if (!element().isValidValue(optionValue))
+        if (!this->element().isValidValue(optionValue))
             continue;
         m_tickMarkValues.append(parseToNumber(optionValue, Decimal::nan()));
     }