Repository: flutter
Issue: Flinging/Scrolling issue when using a list of Slivers and a TabBarView inside of a NestedScrollView.
Labels: framework,f: material design,f: scrolling,a: quality,has reproducible steps,P2,found in release: 2.5,found in release: 2.6,team-design,triaged-design

Flinging a `CustomScrollView` in one of the tabs in a `TabBarView` that's set as the `body` of a `NestedScrollView` that has a list of Slivers in its `headerSliverBuilder` causes stuttering and doesn't smoothly expand the `SliverAppBar` as expected.

## Steps to Reproduce

I've put together a sample app that demonstrates the issue.
You can find the [repository here](https://github.com/omarsahl/live_football_scrolling_poc)

**Expected results:** The `SliverAppBar` should smoothly expand in response to flinging the inner scroll view.

**Actual results:** The UI doesn't scroll smoothly and the `SliverAppBar` doesn't smoothly expand as expected.

Take a look at the video below and you'll notice that when scrolling up the _Lineups_ or the _Commentaries_ tabs, the `SliverAppBar` expands after a pause.

https://user-images.githubusercontent.com/20464116/133216887-e111c9c4-09b6-43c8-83e2-9d2cf536958e.mp4

<details>
  <summary>Logs</summary>

```
flutter analyze

Analyzing live_football_scrolling_poc...
No issues found! (ran in 1.8s)
```

```
flutter doctor -v

[√] Flutter (Channel stable, 2.2.3, on Microsoft Windows [Version 10.0.19043.1165], locale en-US)
    • Flutter version 2.2.3 at C:\flutter
    • Framework revision f4abaa0735 (3 months ago), 2021-07-01 12:46:11 -0700
    • Engine revision 241c87ad80
    • Dart version 2.13.4

[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\Android\sdk
    • Platform android-30, build-tools 30.0.3
    • ANDROID_HOME = C:\Android\sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6842174)
    X Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/windows#android-setup for more details.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

[√] Android Studio (version 4.1.0)
    • Android Studio at C:\Program Files\Android\Android Studio
    • 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 11.0.8+10-b944.6842174)

[√] IntelliJ IDEA Community Edition (version 2020.3)
    • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.2.4
    • 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

[√] VS Code (version 1.60.0)
    • VS Code at C:\Users\Omar\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension can be installed from:
       https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[√] Connected device (3 available)
    • Nokia 7 1 (mobile) • CTLGAP58A1500315 • android-arm64  • Android 10 (API 29)
    • Chrome (web)       • chrome           • web-javascript • Google Chrome 93.0.4577.63
    • Edge (web)         • edge             • web-javascript • Microsoft Edge 93.0.961.47

! Doctor found issues in 1 category.
```

</details>