Implement GetComputedRole in wd (#36552)

Implement Webdriver Get Computed Role.

[spec](https://w3c.github.io/webdriver/#get-computed-role)

Signed-off-by: Kenzie Raditya Tirtarahardja <kenzieradityatirtarahardja.18@gmail.com>
Co-authored-by: Kenzie Raditya Tirtarahardja <kenzieradityatirtarahardja.18@gmail.com>

components/script/script_thread.rs

@@ -2253,6 +2253,14 @@ impl ScriptThread {
             WebDriverScriptCommand::GetActiveElement(reply) => {
                 webdriver_handlers::handle_get_active_element(&documents, pipeline_id, reply)
             },
+            WebDriverScriptCommand::GetComputedRole(node_id, reply) => {
+                webdriver_handlers::handle_get_computed_role(
+                    &documents,
+                    pipeline_id,
+                    node_id,
+                    reply,
+                )
+            },
             WebDriverScriptCommand::GetPageSource(reply) => {
                 webdriver_handlers::handle_get_page_source(&documents, pipeline_id, reply, can_gc)
             },

components/script/webdriver_handlers.rs

@@ -799,6 +799,24 @@ pub(crate) fn handle_get_active_element(
         .unwrap();
 }
 
+pub(crate) fn handle_get_computed_role(
+    documents: &DocumentCollection,
+    pipeline: PipelineId,
+    node_id: String,
+    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
+) {
+    reply
+        .send(
+            find_node_by_unique_id(documents, pipeline, node_id).and_then(|node| {
+                match node.downcast::<Element>() {
+                    Some(element) => Ok(element.GetRole().map(String::from)),
+                    None => Err(ErrorStatus::UnknownError),
+                }
+            }),
+        )
+        .unwrap();
+}
+
 pub(crate) fn handle_get_page_source(
     documents: &DocumentCollection,
     pipeline: PipelineId,

components/shared/embedder/webdriver.rs

@@ -114,6 +114,7 @@ pub enum WebDriverScriptCommand {
     FocusElement(String, IpcSender<Result<(), ErrorStatus>>),
     ElementClick(String, IpcSender<Result<Option<String>, ErrorStatus>>),
     GetActiveElement(IpcSender<Option<String>>),
+    GetComputedRole(String, IpcSender<Result<Option<String>, ErrorStatus>>),
     GetCookie(String, IpcSender<Vec<Serde<Cookie<'static>>>>),
     GetCookies(IpcSender<Vec<Serde<Cookie<'static>>>>),
     GetElementAttribute(

components/webdriver_server/lib.rs

@@ -1214,6 +1214,18 @@ impl Handler {
         )))
     }
 
+    fn handle_computed_role(&self, element: &WebElement) -> WebDriverResult<WebDriverResponse> {
+        let (sender, receiver) = ipc::channel().unwrap();
+        let cmd = WebDriverScriptCommand::GetComputedRole(element.to_string(), sender);
+        self.browsing_context_script_command(cmd)?;
+        match receiver.recv().unwrap() {
+            Ok(value) => Ok(WebDriverResponse::Generic(ValueResponse(
+                serde_json::to_value(value)?,
+            ))),
+            Err(error) => Err(WebDriverError::new(error, "")),
+        }
+    }
+
     fn handle_element_tag_name(&self, element: &WebElement) -> WebDriverResult<WebDriverResponse> {
         let (sender, receiver) = ipc::channel().unwrap();
         let cmd = WebDriverScriptCommand::GetElementTagName(element.to_string(), sender);
@@ -1844,6 +1856,7 @@ impl WebDriverHandler<ServoExtensionRoute> for Handler {
             WebDriverCommand::GetNamedCookie(name) => self.handle_get_cookie(name),
             WebDriverCommand::GetCookies => self.handle_get_cookies(),
             WebDriverCommand::GetActiveElement => self.handle_active_element(),
+            WebDriverCommand::GetComputedRole(ref element) => self.handle_computed_role(element),
             WebDriverCommand::GetElementRect(ref element) => self.handle_element_rect(element),
             WebDriverCommand::GetElementText(ref element) => self.handle_element_text(element),
             WebDriverCommand::GetElementTagName(ref element) => {