Repository: flutter
Issue: [web] Button becomes un-tappable in Flutter Web when a TextField is present.
Labels: a: text input,engine,P1,team-web,triaged-web

An internal customer reported (b/350613557) a problem with text fields and buttons (and routes) in the flutter web canvaskit renderer.

<details>
<summary><tt>lib/main.dart</tt></summary>


```dart
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

void main() async {
  runApp(
    MyApp(),
  );
}

final goRouter = GoRouter(
  routes: [
    GoRoute(
      path: '/',
      builder: (context, state) => Scaffold(
        body: Center(
          child: TextButton(
            onPressed: () => context.go('/next'),
            child: Text('Next'),
          ),
        ),
      ),
    ),
    GoRoute(
      path: '/next',
      builder: (context, state) => MyHomePage(
        title: 'Next page',
      ),
    ),
  ],
);

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      title: 'Flutter Demo',
      routerConfig: goRouter,
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(
          widget.title,
        ),
        automaticallyImplyLeading: false,
        leading: BackButton(
          onPressed: () {
            context.go('/');
          },
        ),
      ),
      body: Column(
        children: [
          TextField(
            autofocus: true,
          ),
        ],
      ),
    );
  }
}
```

</details>

<details>
<summary><tt>web/index.html</tt></summary>

```html
<html>
  <head>
    <script src="flutter.js" defer></script>
  </head>
  <body>
    <script>
      window.addEventListener('load', function (ev) {
        _flutter.loader.loadEntrypoint({
          entrypointUrl: 'main.dart.js',
          onEntrypointLoaded: function(engineInitializer) {
            engineInitializer.initializeEngine().then(function(appRunner) {
              appRunner.runApp();
            });
          }
        });
      });
   </script>
  </body>
</html>
```

</details>

To reproduce:

1. Navigate to and from the nested route using the buttons.
2. Focus, unfocus the text field.
3. Repeat.

Observed behavior:

* Button becomes unresponsive very soon. It happens sooner or later.
* Exceptions:

```
 (errors.dart:296:3)
    at Object.assertFailed (errors.dart:29:3)
    at Object._computeOffsetForInputs (event_position_helper.dart:64:37)
    at Object.computeEventOffsetToTarget (event_position_helper.dart:32:14)
    at [_convertEventsToPointerData] (pointer_binding.dart:1062:30)
    at pointer_binding.dart:1001:9
    at pointer_binding.dart:939:7
    at loggedHandler (pointer_binding.dart:532:9)
    at Object._callDartFunctionFast1 (js_allow_interop_patch.dart:188:27)
    at ret (js_allow_interop_patch.dart:81:15)
```