LibWeb: Added HTMLLinkElement.as

Author: https://github.com/Hexeption
Commit: 2f4668edce
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/39
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/nico

Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp

@@ -90,6 +90,29 @@ void HTMLLinkElement::inserted()
     }
 }
 
+// https://html.spec.whatwg.org/multipage/semantics.html#dom-link-as
+String HTMLLinkElement::as() const
+{
+    String attribute_value = get_attribute_value(HTML::AttributeNames::as);
+
+    if (attribute_value.equals_ignoring_ascii_case("fetch"sv) ||
+        attribute_value.equals_ignoring_ascii_case("image"sv) ||
+        attribute_value.equals_ignoring_ascii_case("script"sv) ||
+        attribute_value.equals_ignoring_ascii_case("style"sv) ||
+        attribute_value.equals_ignoring_ascii_case("video"sv) ||
+        attribute_value.equals_ignoring_ascii_case("audio"sv) ||
+        attribute_value.equals_ignoring_ascii_case("track"sv) ||
+        attribute_value.equals_ignoring_ascii_case("font"sv))
+        return attribute_value.to_lowercase().release_value();
+
+    return String {};
+}
+
+WebIDL::ExceptionOr<void> HTMLLinkElement::set_as(String const& value)
+{
+    return set_attribute(HTML::AttributeNames::as, move(value));
+}
+
 // https://html.spec.whatwg.org/multipage/semantics.html#dom-link-rellist
 JS::NonnullGCPtr<DOM::DOMTokenList> HTMLLinkElement::rel_list()
 {