adding click event for removal. adding unit tests

Author: nturgut

lib/web_ui/lib/src/engine/semantics/semantics_helper.dart

@@ -256,9 +256,11 @@ class MobileSemanticsEnabler extends SemanticsEnabler {
   @override
   bool tryEnableSemantics(html.Event event) {
     if (_schedulePlaceholderRemoval) {
+      // The event type can also be click for VoiceOver.
       final bool removeNow = (browserEngine != BrowserEngine.webkit ||
           event.type == 'touchend' ||
-          event.type == 'pointerup');
+          event.type == 'pointerup' ||
+          event.type == 'click');
       if (removeNow) {
         _semanticsPlaceholder!.remove();
         _semanticsPlaceholder = null;

lib/web_ui/test/engine/semantics/semantics_helper_test.dart

@@ -9,6 +9,8 @@ import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
 import 'package:ui/src/engine.dart';
 
+const PointerSupportDetector _defaultSupportDetector = PointerSupportDetector();
+
 void main() {
   internalBootstrapBrowserTest(() => testMain);
 }
@@ -151,15 +153,31 @@ void testMain() {
         skip: browserEngine == BrowserEngine.webkit);
 
     test('Not relevant events should be forwarded to the framework', () async {
-      final html.Event event = html.TouchEvent('touchcancel');
+      html.Event event;
+      if (_defaultSupportDetector.hasPointerEvents) {
+         event = html.PointerEvent('pointerdown');
+      } else if(_defaultSupportDetector.hasTouchEvents) {
+         event = html.TouchEvent('touchcancel');
+      } else {
+         event = html.MouseEvent('mousemove');
+      }
+
       bool shouldForwardToFramework =
           mobileSemanticsEnabler.tryEnableSemantics(event);
 
       expect(shouldForwardToFramework, true);
     },
-        // TODO(nurhan): https://github.com/flutter/flutter/issues/50590
-        // TODO(nurhan): https://github.com/flutter/flutter/issues/46638
-        // TODO(nurhan): https://github.com/flutter/flutter/issues/50754
-        skip: browserEngine != BrowserEngine.blink);
+        skip: browserEngine == BrowserEngine.edge);
+
+    test('Pointer down is relevant event', () async {
+      expect(mobileSemanticsEnabler.semanticsActivationAttempts, isZero);
+
+      final html.Event event = html.PointerEvent('pointerdown');
+      mobileSemanticsEnabler.tryEnableSemantics(event);
+
+      expect(mobileSemanticsEnabler.semanticsActivationAttempts, isNonZero);
+    },
+        skip: browserEngine == BrowserEngine.edge ||
+              browserEngine == BrowserEngine.firefox);
   });
 }