Repository: flutter
Issue: LongPressDraggable.onDragUpdate stops being called after updating ScrollController
Labels: framework,f: scrolling,f: gestures,has reproducible steps,P2,found in release: 3.3,found in release: 3.7,team-framework,triaged-framework

I'm trying to use a `LongPressDraggable` which, when dragged towards the top of the screen, triggers `animateTo()` to make the `ListView` scroll up so that the item can be dragged all the way to the top of the list.

Problem is on some items (specially the ones more towards the end of the list), after dragging the item for a while, the `onDragUpdate` callback stops being called so I can't keep updating the scroll controller.

I've made a simple app to show the behaviour:
https://github.com/giorgenes/flutter-draggable-scrollable-bug/blob/main/lib/main.dart


## Steps to Reproduce

1. Run the app above (I'm running on a physical pixel 3 device).
2. Long press the last item (item 9) and scroll it to the top on top of the title bar.
3. Keep holding the item there as the scroll is updated and scroll up.
4. Observe that the listView doesn't reach the top and stops just before reaching the top, after which the `onDragUpdate` stops being called as seen in the console logs.
5. Observe that no matter where you move the item afterwards, the callback is not called anymore.

**Expected results:** <!-- what did you want to see? -->
`onDragUpdate` should never stop being called.


**Actual results:** <!-- what did you see? -->

`onDragUpdate` stops being called when interacting with the scroll controller.


<details>
  <summary>Logs</summary>

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```
[✓] Flutter (Channel stable, 2.2.0, on Mac OS X 10.15.7 19H524 darwin-x64, locale en-AU)
    • Flutter version 2.2.0 at /Users/giorgenes/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 30.0.3)
    • Android SDK at /Users/giorgenes/Library/Android/sdk
    • Platform android-30, build-tools 30.0.3
    • 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 1.56.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.22.0

[✓] Connected device (2 available)
    • Pixel 3 (mobile) • 192.168.0.5:5555 • android-arm64  • Android 11 (API 30)
    • Chrome (web)     • chrome           • web-javascript • Google Chrome 90.0.4430.212

• No issues found!
```

</details>