webdriver: Implement send alert text (#38140)

Implement webdriver `SendAlertText` command

Tests:
https://github.com/longvatrong111/servo/actions/runs/16342669929
https://github.com/longvatrong111/servo/actions/runs/16342671477

cc: @xiaochengh

---------

Signed-off-by: batu_hoang <hoang.binh.trong@huawei.com>
Signed-off-by: batu_hoang <longvatrong111@gmail.com>

ports/servoshell/desktop/app.rs

@@ -620,6 +620,9 @@ impl App {
                         warn!("Failed to send response of GetAlertText: {error}");
                     };
                 },
+                WebDriverCommandMsg::SendAlertText(webview_id, text) => {
+                    running_state.set_alert_text_of_newest_dialog(webview_id, text);
+                },
                 WebDriverCommandMsg::TakeScreenshot(..) => {
                     warn!(
                         "WebDriverCommand {:?} is still not moved from constellation to embedder",

ports/servoshell/desktop/app_state.rs

@@ -381,6 +381,14 @@ impl RunningAppState {
             .and_then(|dialog| dialog.message())
     }
 
+    pub(crate) fn set_alert_text_of_newest_dialog(&self, webview_id: WebViewId, text: String) {
+        if let Some(dialogs) = self.inner_mut().dialogs.get_mut(&webview_id) {
+            if let Some(dialog) = dialogs.last_mut() {
+                dialog.set_message(text);
+            }
+        }
+    }
+
     pub(crate) fn get_focused_webview_index(&self) -> Option<usize> {
         let focused_id = self.inner().focused_webview_id?;
         self.webviews()

ports/servoshell/desktop/dialog.rs

@@ -168,6 +168,12 @@ impl Dialog {
         }
     }
 
+    pub fn set_message(&mut self, text: String) {
+        if let Dialog::SimpleDialog(dialog) = self {
+            dialog.set_message(text);
+        }
+    }
+
     pub fn update(&mut self, ctx: &egui::Context) -> bool {
         match self {
             Dialog::File {