[engine] force semantics action to post a task.

[jonahwilliams]

Repro:

Testing WIP.

b/373761573

import 'package:flutter/material.dart';

void main() {
  runApp(const Example());
}

class Example extends StatefulWidget {
  const Example({super.key});

  @override
  State<Example> createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
  bool value = true;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: Semantics(
            child: Text(
              value ? 'Hello, world!' : 'Goodbye, World!',
            ),
            button: true,
            onTap: () async {
              await null;
              setState(() {
                value = !value;
              });
            },
          ),
        ),
      ),
      );
  }
}

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!).

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Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

[jonahwilliams]

I wired up a test to verify this behavior but found that it was passing anyway. I don't know if this is due to the test environment, but 🤷‍♂️

[auto-submit]

auto label is removed for flutter/engine/56514, due to - The status or check suite Linux linux_unopt has failed. Please fix the issues identified (or deflake) before re-applying this label.

[auto-submit]

auto label is removed for flutter/engine/56514, due to - The status or check suite Mac mac_host_engine has failed. Please fix the issues identified (or deflake) before re-applying this label.