webdriver: consider boolean attribute when get element attribute (#38401)

The function handle_get_attribute should act differently when the
attribute is a boolean attribute.

The full list of attributes can be found in [1]. All attributes marked
as "Boolean attribute" in the "Value" column are boolean attributes.
Note that "hidden" is effectively treated as a boolean attribute,
according to WPT test "test_global_boolean_attributes" in
webdriver/tests/classic/get_element_attribute/get.py

[1] https://html.spec.whatwg.org/multipage/#attributes-3

Testing: Updated WPT test expectation
Fixes: #38353

---------

Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>

components/script/dom/attr.rs

@@ -289,3 +289,47 @@ pub(crate) fn is_relevant_attribute(namespace: &Namespace, local_name: &LocalNam
     // <https://svgwg.org/svg2-draft/linking.html#XLinkHrefAttribute>
     namespace == &ns!() || (namespace == &ns!(xlink) && local_name == &local_name!("href"))
 }
+
+/// A help function to check if an attribute is a boolean attribute.
+pub(crate) fn is_boolean_attribute(name: &str) -> bool {
+    // The full list of attributes can be found in [1]. All attributes marked as "Boolean
+    // attribute" in the "Value" column are boolean attributes. Note that "hidden" is effectively
+    // treated as a boolean attribute, according to WPT test "test_global_boolean_attributes" in
+    // webdriver/tests/classic/get_element_attribute/get.py
+    //
+    // [1] <https://html.spec.whatwg.org/multipage/#attributes-3>
+    [
+        "allowfullscreen",
+        "alpha",
+        "async",
+        "autofocus",
+        "autoplay",
+        "checked",
+        "controls",
+        "default",
+        "defer",
+        "disabled",
+        "formnovalidate",
+        "hidden",
+        "inert",
+        "ismap",
+        "itemscope",
+        "loop",
+        "multiple",
+        "muted",
+        "nomodule",
+        "novalidate",
+        "open",
+        "playsinline",
+        "readonly",
+        "required",
+        "reversed",
+        "selected",
+        "shadowrootclonable",
+        "shadowrootcustomelementregistry",
+        "shadowrootdelegatesfocus",
+        "shadowrootserializable",
+    ]
+    .iter()
+    .any(|&boolean_attr| boolean_attr.eq_ignore_ascii_case(name))
+}