Repository: flutter
Issue: [A11y]: Slider labels not included in the `Semantics` widget
Labels: in triage

### Steps to reproduce

When creating `Slider` widgets, the `Slider.label` information isn't passed to the semantics widget.

### Expected results

Sliders should announce their labels when tabbing through with a screen reader such as NVDA. I can't test platforms other than Windows or Chrome while at work.

### Actual results

NVDA announces "Slider", then the percentage.

The third slider works perfectly. Looking at the implementation of the `Slider` widget, it seems that there is no `label` property being passed to the `Semantics` widget at the end of the `_buildMaterialSlider` method.

I've tested this locally, and adding the `label` argument fixes this.
Am I OK to submit a PR with this change? I don't really know how all of this works. I'm keen to help, but - depending on how much vetting I'll need - it might be quicker for someone else to add `label: widget.label` to line 1083 of `slider.dart`. 😄

Thank you for a wonderful framework!!

### Code sample

<details open><summary>Code sample</summary>

```dart
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    final renderBinding = RendererBinding.instance;
    if (!renderBinding.semanticsEnabled) {
      renderBinding.ensureSemantics();
    }
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    const divider = 100;
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text('$_counter'),
            Slider(
              autofocus: true,
              value: _counter / divider,
              onChanged: (value) => setState(
                () => _counter = (value * divider).round(),
              ),
              label: 'Screen readers will not pick up this label',
            ),
            Slider(
              value: _counter / divider,
              onChanged: (value) => setState(
                () => _counter = (value * divider).round(),
              ),
              label: 'Screen readers will not speak this label either',
              semanticFormatterCallback: (value) =>
                  'Screen readers will show this value. Counter is $_counter',
            ),
            MergeSemantics(
              // I use `MergeSemantics` to prevent NVDA from recognising a group.
              child: Semantics(
                label: 'This works perfectly',
                child: Slider(
                  value: _counter / divider,
                  onChanged: (value) => setState(
                    () => _counter = (value * divider).round(),
                  ),
                  label:
                      'We just need to wrap the `Slider` widget in a `MergeSemantics` and a `Semantics` widget and everything will be fixed',
                ),
              ),
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}
```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details open><summary>Logs</summary>

```console
```

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[Γ£ô] Flutter (Channel master, 3.28.0-2.0.pre.38833, on Microsoft Windows [Version 10.0.26100.2894], locale en-GB) [2.5s]
    ΓÇó Flutter version 3.28.0-2.0.pre.38833 on channel master at C:\Users\chris\flutter
    ΓÇó Upstream repository https://github.com/flutter/flutter
    ΓÇó Framework revision 97ca57cf08 (6 hours ago), 2025-01-23 06:38:20 +0100
    ΓÇó Engine revision 97ca57cf08
    ΓÇó Dart version 3.8.0 (build 3.8.0-24.0.dev)
    ΓÇó DevTools version 2.42.0

[Γ£ô] Windows Version (11 Home 64-bit, 24H2, 2009) [4.1s]

[Γ£ô] Android toolchain - develop for Android devices (Android SDK version 34.0.0) [4.4s]
    ΓÇó Android SDK at C:\Users\chris\AppData\Local\Android\sdk
    ΓÇó Platform android-35, build-tools 34.0.0
    ΓÇó Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    ΓÇó Java version OpenJDK Runtime Environment (build 17.0.6+0-b2043.56-9586694)
    ΓÇó All Android licenses accepted.

[Γ£ô] Chrome - develop for the web [119ms]
    ΓÇó Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[Γ£ô] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.12.4) [117ms]
    ΓÇó Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    ΓÇó Visual Studio Community 2022 version 17.12.35707.178
    ΓÇó Windows 10 SDK version 10.0.22621.0

[Γ£ô] Android Studio (version 2022.2) [16ms]
    ΓÇó Android Studio at C:\Program Files\Android\Android Studio
    ΓÇó Flutter plugin can be installed from:
      ≡ƒö¿ https://plugins.jetbrains.com/plugin/9212-flutter
    ΓÇó Dart plugin can be installed from:
      ≡ƒö¿ https://plugins.jetbrains.com/plugin/6351-dart
    ΓÇó Java version OpenJDK Runtime Environment (build 17.0.6+0-b2043.56-9586694)

[Γ£ô] VS Code, 64-bit edition (version 1.96.2) [14ms]
    ΓÇó VS Code at C:\Program Files\Microsoft VS Code
    ΓÇó Flutter extension version 3.102.0

[Γ£ô] Connected device (3 available) [290ms]
    ΓÇó Windows (desktop) ΓÇó windows ΓÇó windows-x64    ΓÇó Microsoft Windows [Version 10.0.26100.2894]
    ΓÇó Chrome (web)      ΓÇó chrome  ΓÇó web-javascript ΓÇó Google Chrome 131.0.6778.265
    ΓÇó Edge (web)        ΓÇó edge    ΓÇó web-javascript ΓÇó Microsoft Edge 132.0.2957.115

[Γ£ô] Network resources [412ms]
    ΓÇó All expected network resources are available.

ΓÇó No issues found!
```

</details>