[web] Fix done button click not blur in iOS keyboard (#96357)

Author: JunbinDeng

lib/web_ui/lib/src/engine/text_editing/text_editing.dart

@@ -1453,23 +1453,12 @@ class IOSTextEditingStrategy extends GloballyPositionedTextEditingStrategy {
 
     _addTapListener();
 
-    // On iOS, blur is trigerred in the following cases:
-    //
-    // 1. The browser app is sent to the background (or the tab is changed). In
-    //    this case, the window loses focus (see [windowHasFocus]),
-    //    so we close the input connection with the framework.
-    // 2. The user taps on another focusable element. In this case, we refocus
-    //    the input field and wait for the framework to manage the focus change.
-    // 3. The virtual keyboard is closed by tapping "done". We can't detect this
-    //    programmatically, so we end up refocusing the input field. This is
-    //    okay because the virtual keyboard will hide, and as soon as the user
-    //    taps the text field again, the virtual keyboard will come up.
+    // On iOS, blur is trigerred if the virtual keyboard is closed or the
+    // browser is sent to background or the browser tab is changed.
     subscriptions.add(activeDomElement.onBlur.listen((_) {
-      if (windowHasFocus) {
-        activeDomElement.focus();
-      } else {
+      Future<void>.delayed(Duration.zero, () {
         owner.sendTextConnectionClosedToFrameworkIfAny();
-      }
+      });
     }));
   }
 

lib/web_ui/test/text_editing_test.dart

@@ -665,12 +665,25 @@ void testMain() {
       // DOM element is blurred.
       textEditing!.strategy.domElement!.blur();
 
-      // No connection close message sent.
-      expect(spy.messages, hasLength(0));
-      await Future<void>.delayed(Duration.zero);
-      // DOM element still keeps the focus.
-      expect(defaultTextEditingRoot.activeElement,
-          textEditing!.strategy.domElement);
+      // For ios-safari the connection is closed.
+      if (browserEngine == BrowserEngine.webkit &&
+          operatingSystem == OperatingSystem.iOs) {
+        await Future<void>.delayed(Duration.zero);
+        expect(spy.messages, hasLength(1));
+        expect(spy.messages[0].channel, 'flutter/textinput');
+        expect(
+            spy.messages[0].methodName, 'TextInputClient.onConnectionClosed');
+        await Future<void>.delayed(Duration.zero);
+        // DOM element loses the focus.
+        expect(defaultTextEditingRoot.activeElement, null);
+      } else {
+        // No connection close message sent.
+        expect(spy.messages, hasLength(0));
+        await Future<void>.delayed(Duration.zero);
+        // DOM element still keeps the focus.
+        expect(defaultTextEditingRoot.activeElement,
+            textEditing!.strategy.domElement);
+      }
     },
         // TODO(mdebbar): https://github.com/flutter/flutter/issues/50769
         skip: browserEngine == BrowserEngine.edge);