Repository: flutter
Issue: [Flutter Web] SelectableText selection background is off when a height is set
Labels: framework,engine,f: material design,a: typography,has reproducible steps,P2,found in release: 2.2,team-design,triaged-design

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## Steps to Reproduce

<!-- You must include full steps to reproduce so that we can reproduce the problem. -->
Set a value to the height parameter in TextStyle

```
class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        SelectableText(
          'SelectableText with no height',
          style: TextStyle(),
        ),
        SizedBox(height: 16),
        SelectableText(
          'SelectableText with height',
          style: TextStyle(height: 1),
        ),
      ],
    );
  }
}
```

**Expected results:** <!-- what did you want to see? -->

![21622334889_ pic](https://user-images.githubusercontent.com/7555373/120088603-b213c680-c135-11eb-96d5-6ab1f3cc23a2.jpg)

**Actual results:** <!-- what did you see? -->

![11622334858_ pic](https://user-images.githubusercontent.com/7555373/120088606-b6d87a80-c135-11eb-96f4-3021b6390379.jpg)

<details>
  <summary>Logs</summary>

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```
```

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```
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
[✓] Flutter (Channel stable, 2.2.0, on macOS 11.2.2 20D80 darwin-x64, locale en-AU)
    • Flutter version 2.2.0 at /Users/edwin/flutter
    • Framework revision b22742018b (2 weeks ago), 2021-05-14 19:12:57 -0700
    • Engine revision a9d88a4d18
    • Dart version 2.13.0

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/edwin/Library/Android/sdk
    • Platform android-30, build-tools 29.0.2
    • 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 at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.5, Build version 12E262
    • CocoaPods version 1.10.1

[✓] 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 1.56.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.22.0

[✓] Connected device (1 available)
    • Chrome (web) • chrome • web-javascript • Google Chrome 91.0.4472.77
```

</details>