Repository: flutter
Issue: [web]Display keyboard unable to click on other textfield on safari browser.
Labels: a: text input,platform-ios,platform-web,e: OS-version specific,has reproducible steps,P3,browser: safari-ios,team-framework,triaged-framework,found in release: 3.19,found in release: 3.20

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After the keyboard is displayed in the safari browser, I can't click on the other textfield,. I find this problem on both IOS11 and 12.

Example:

```dart
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, 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),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextField(),
            TextField(),
            TextField(),
            TextField(),
            TextField(),
            TextField(),
          ],
        ),
      ),
    );
  }
}
```


**Expected results:** <!-- what did you want to see? -->

You can switch between textfield and button when the keyboard is displayed.

**Actual results:** <!-- what did you see? -->

No other button or textfield can be clicked after the keyboard is displayed.

<details>
  <summary>Logs</summary>

<!--
      Run your application with `flutter run --verbose` and attach all the
      log output below between the lines with the backticks. If there is an
      exception, please see if the error message includes enough information
      to explain how to solve the issue.
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```
```

<!--
     Run `flutter analyze` and attach any output of that command below.
     If there are any analysis errors, try resolving them before filing this issue.
-->

```
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
[✓] Flutter (Channel dev, 1.19.0-0.0.pre, on Mac OS X 10.14.6 18G84, locale zh-Hans-CN)
    • Flutter version 1.19.0-0.0.pre at /Users/ming/flutter
    • Framework revision a849daf283 (3 weeks ago), 2020-05-07 18:59:02 -0700
    • Engine revision 3953c3ccd1
    • Dart version 2.9.0 (build 2.9.0-5.0.dev 4da5b40fb6)

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/ming/Library/Android/sdk
    • Platform android-29, build-tools 29.0.2
    • ANDROID_HOME = /Users/ming/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.3, Build version 11C29
    • CocoaPods version 1.9.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 39.0.3
    • Dart plugin version 191.8423
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[✓] VS Code (version 1.45.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.10.2

[✓] Connected device (3 available)
    • SM N9700   • R58M84RVP3D • android-arm64  • Android 10 (API 29)
    • Web Server • web-server  • web-javascript • Flutter Tools
    • Chrome     • chrome      • web-javascript • Google Chrome 83.0.4103.61
```

</details>