Repository: flutter
Issue: IntrinsicWidth doesn't honor errorText of TextFormField
Labels: a: text input,framework,f: material design,has reproducible steps,found in release: 2.1,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. -->

1. Run `flutter create bug`.
2. Change the main page to:
```
class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: IntrinsicWidth(
          child: TextFormField(
            initialValue: 'empty',
            decoration: InputDecoration(
              isDense: true,
              border: UnderlineInputBorder(),
              errorText: 'Some error got trucked',
            ),
          ),
        ),
      ),
    );
  }
}
```

**Expected results:**
The error message should not be trucked. Is this a bug or expected behavior? Appears on both mobile and web.

<img height="720" src="https://user-images.githubusercontent.com/47757556/110264527-54287600-7f6e-11eb-8d18-d8c1cdbe143c.png">



```
flutter doctor -v
[✓] Flutter (Channel dev, 2.1.0-10.0.pre, on Mac OS X 10.15.7 19H15 darwin-x64, locale en-GB)
    • Flutter version 2.1.0-10.0.pre at /Users/maple/work/flutter
    • Framework revision cc9b78fc5c (10 days ago), 2021-02-25 13:26:03 -0800
    • Engine revision a252ec09b7
    • Dart version 2.13.0 (build 2.13.0-77.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/maple/Library/Android/sdk
    • Platform android-30, build-tools 29.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.4, Build version 12D4e
    • CocoaPods version 1.10.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)

[✓] VS Code (version 1.54.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.20.0

[✓] Connected device (1 available)
    • Chrome (web) • chrome • web-javascript • Google Chrome 88.0.4324.192

• No issues found!
```