script: Support decomposing ShadowRoot from mozjs HandleValue (#38984)

- Add `ShadowRoot` to `JSValue` to avoid
`WebDriverJSError::UnknownType`, and
`JavaScriptEvaluationError::SerializationError` when execute JS from
embedder.
- Add unit test.
- Move [is_detached](https://w3c.github.io/webdriver/#dfn-is-detached)
to `fn is_detached` to be reused.
- Other random simplification.

Testing: WebDriver conformance tests.

---------

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

components/script/dom/htmlelement.rs

@@ -617,7 +617,7 @@ impl HTMLElementMethods<crate::DomTypeHolder> for HTMLElement {
         // Note: the element can pass this check without yet being a custom
         // element, as long as there is a registered definition
         // that could upgrade it to one later.
-        let registry = self.owner_document().window().CustomElements();
+        let registry = self.owner_window().CustomElements();
         let definition = registry.lookup_definition(self.as_element().local_name(), None);
 
         // Step 3: If definition is null, then throw an "NotSupportedError" DOMException

components/script/dom/node.rs

@@ -1282,7 +1282,7 @@ impl Node {
     pub(crate) fn summarize(&self, can_gc: CanGc) -> NodeInfo {
         let USVString(base_uri) = self.BaseURI();
         let node_type = self.NodeType();
-        let pipeline = self.owner_document().window().pipeline_id();
+        let pipeline = self.owner_window().pipeline_id();
 
         let maybe_shadow_root = self.downcast::<ShadowRoot>();
         let shadow_root_mode = maybe_shadow_root

components/script/webdriver_handlers.rs

@@ -95,6 +95,13 @@ fn is_stale(element: &Element) -> bool {
     !element.owner_document().is_active() || !element.is_connected()
 }
 
+/// <https://w3c.github.io/webdriver/#dfn-is-detached>
+fn is_detached(shadow_root: &ShadowRoot) -> bool {
+    // A shadow root is detached if its node document is not the active document
+    // or if the element node referred to as its host is stale.
+    !shadow_root.owner_document().is_active() || is_stale(&shadow_root.Host())
+}
+
 /// <https://w3c.github.io/webdriver/#dfn-disabled>
 fn is_disabled(element: &Element) -> bool {
     // Step 1. If element is an option element or element is an optgroup element
@@ -173,12 +180,7 @@ fn get_known_shadow_root(
     // A shadow root is detached if its node document is not the active document
     // or if the element node referred to as its host is stale.
     let shadow_root = DomRoot::downcast::<ShadowRoot>(node).unwrap();
-    if !shadow_root.owner_document().is_active() {
-        return Err(ErrorStatus::DetachedShadowRoot);
-    }
-
-    let host = shadow_root.Host();
-    if is_stale(&host) {
+    if is_detached(&shadow_root) {
         return Err(ErrorStatus::DetachedShadowRoot);
     }
     // Step 5. Return success with data node.
@@ -396,15 +398,27 @@ unsafe fn jsval_to_webdriver_inner(
         });
         let _ac = JSAutoRealm::new(cx, *object);
 
-        // TODO: special handling for ShadowRoot
         if let Ok(element) = root_from_object::<Element>(*object, cx) {
             // If the element is stale, return error with error code stale element reference.
             if is_stale(&element) {
                 Err(WebDriverJSError::StaleElementReference)
             } else {
-                Ok(JSValue::Element(element.upcast::<Node>().unique_id(
-                    element.owner_document().window().pipeline_id(),
-                )))
+                Ok(JSValue::Element(
+                    element
+                        .upcast::<Node>()
+                        .unique_id(element.owner_window().pipeline_id()),
+                ))
+            }
+        } else if let Ok(shadow_root) = root_from_object::<ShadowRoot>(*object, cx) {
+            // If the shadow root is detached, return error with error code detached shadow root.
+            if is_detached(&shadow_root) {
+                Err(WebDriverJSError::DetachedShadowRoot)
+            } else {
+                Ok(JSValue::ShadowRoot(
+                    shadow_root
+                        .upcast::<Node>()
+                        .unique_id(shadow_root.owner_window().pipeline_id()),
+                ))
             }
         } else if let Ok(window) = root_from_object::<Window>(*object, cx) {
             let window_proxy = window.window_proxy();