Repository: flutter
Issue: [desktop]: Screen doesn't scroll with trackpad if pointer is placed on scrollbar and then try to scroll.
Labels: framework,f: scrolling,a: desktop,has reproducible steps,P3,team-framework,triaged-framework,found in release: 3.24,found in release: 3.27

### Steps to reproduce

1. Run the sample
2. Move the cursor to the edge to show the dragbar (over the dragbar)
3. Scroll on touchpad

### Expected results

Widget also scrolls.

### Actual results

The widget does not scroll.

Windows and MacOS have this issue.
I have no Linux touchpad to test.

### Code sample

<details open><summary>Code sample</summary>

```dart
import 'package:flutter/material.dart';

/// Flutter code sample for [SingleChildScrollView].

void main() => runApp(const SingleChildScrollViewExampleApp());

class SingleChildScrollViewExampleApp extends StatelessWidget {
  const SingleChildScrollViewExampleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: SingleChildScrollViewExample(),
    );
  }
}

class SingleChildScrollViewExample extends StatelessWidget {
  const SingleChildScrollViewExample({super.key});

  @override
  Widget build(BuildContext context) {
    return DefaultTextStyle(
      style: Theme.of(context).textTheme.bodyMedium!,
      child: LayoutBuilder(
        builder: (BuildContext context, BoxConstraints viewportConstraints) {
          return SingleChildScrollView(
            child: ConstrainedBox(
              constraints: BoxConstraints(
                minHeight: viewportConstraints.maxHeight,
              ),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                mainAxisAlignment: MainAxisAlignment.spaceAround,
                children: List.generate(10, (int i) {
                  return Container(
                    color: i.isEven
                        ? const Color(0xffeeee00)
                        : const Color(0xff008000),
                    height: 120.0,
                    alignment: Alignment.center,
                    child: Text('List item $i'),
                  );
                }),
              ),
            ),
          );
        },
      ),
    );
  }
}

```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details open><summary>Logs</summary>

```console
[Paste your logs here]
```

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[√] Flutter (Channel stable, 3.24.5, on Microsoft Windows [Version 10.0.22631.4460], locale en-US)
    • Flutter version 3.24.5 on channel stable at D:\DevEnv\flutter\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision dec2ee5c1f (2 weeks ago), 2024-11-13 11:13:06 -0800
    • Engine revision a18df97ca5
    • Dart version 3.5.4
    • DevTools version 2.37.3

[√] Windows Version (Installed version of Windows is version 10 or higher)

[X] Android toolchain - develop for Android devices
    X Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/to/windows-android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.


[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.7.0)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.7.34003.232
    • Windows 10 SDK version 10.0.22621.0

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/to/windows-android-setup for detailed instructions).

[!] Proxy Configuration
    • HTTP_PROXY is set
    ! NO_PROXY is not set

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.22631.4460]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 131.0.6778.86
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 130.0.2849.80

[√] Network resources
    • All expected network resources are available.

! Doctor found issues in 3 categories.
```

</details>