AX: Add waitForNotifications and enhance waitForNotification in accessibility-helper.js

https://bugs.webkit.org/show_bug.cgi?id=306500
<rdar://problem/169155012>

Reviewed by Tyler Wilcock.

Enhance waitForNotification to support global notification listeners when no
specific AccessibilityUIElement is provided. This allows tests to listen for
notifications without knowing which element will emit them.

Add new waitForNotifications function that waits for a specified count of
notifications and invokes a handler callback for each one. This is useful for
tests that need to verify multiple sequential notifications are fired, such as
text selection change tests.

* LayoutTests/resources/accessibility-helper.js:

Canonical link: https://commits.webkit.org/306418@main

Author: AndresGonzalezApple

LayoutTests/resources/accessibility-helper.js

@@ -270,21 +270,73 @@ async function waitForElementById(id) {
 }
 
 // Executes the operation and waits until an accessibility notification of the provided
-// `notificationName` is received. A notification listener is added to the AccessibilityUIElement
-// passed in; before the operation is executed. The `operation` is expected to be a function,
+// `notificationName` is received. A notification listener is added to the passed
+// AccessibilityUIElement if not null, or a global listener is installed, before
+// the operation is executed. The `operation` is expected to be a function,
 // which can optionally be async.
-async function waitForNotification(accessibilityElement, notificationName, operation) {
-    var reached = false;
-    function listener(receivedNotification) {
-        if (receivedNotification == notificationName) {
-            reached = true;
-            accessibilityElement.removeNotificationListener(listener);
-        }
+async function waitForNotification(axElement, notificationName, operation) {
+    var received = false;
+
+    function elementListener(notification) {
+        if (notification != notificationName)
+            return;
+        received = true;
+        axElement.removeNotificationListener(elementListener);
+    }
+
+    function globalListener(element, notification) {
+        if (notification != notificationName)
+            return;
+        received = true;
+        accessibilityController.removeNotificationListener(globalListener);
     }
 
-    accessibilityElement.addNotificationListener(listener);
+    if (axElement)
+        axElement.addNotificationListener(elementListener);
+    else
+        accessibilityController.addNotificationListener(globalListener);
+
+    await operation();
+    await waitFor(() => { return received; });
+}
+
+// Executes the passed operation function and waits for expectedCount number of
+// notifications of the given name. It takes a notificationHandler function to
+// be executed when the proper notifications are received. Similarly to
+// waitForNotification, the listener can be added to the given AccessibilityUIElement
+// or globally.
+async function waitForNotifications(axElement, notificationName, expectedCount, operation, notificationHandler) {
+    var receivedCount = 0;
+
+    function elementListener(notification) {
+        if (notification != notificationName)
+            return;
+        ++receivedCount;
+
+        notificationHandler(axElement, notification);
+
+        if (receivedCount == expectedCount)
+            axElement.removeNotificationListener(elementListener);
+    }
+
+    function globalListener(element, notification) {
+        if (notification != notificationName)
+            return;
+        ++receivedCount;
+
+        notificationHandler(element, notification);
+
+        if (receivedCount == expectedCount)
+            accessibilityController.removeNotificationListener(globalListener);
+    }
+
+    if (axElement)
+        axElement.addNotificationListener(elementListener);
+    else
+        accessibilityController.addNotificationListener(globalListener);
+
     await operation();
-    await waitFor(() => { return reached; });
+    await waitFor(() => { return receivedCount == expectedCount; });
 }
 
 // Expect an expression to equal a value and return the result as a string.