Repository: flutter
Issue: [macOS] `didChangeAccessibilityFeatures` is not being called
Labels: engine,a: accessibility,platform-mac,has reproducible steps,P2,found in release: 3.22,team-macos,triaged-macos,found in release: 3.24

### Steps to reproduce

1. Declare an AppWidget with `WidgetsBindingObserver` that returns a MaterialApp/CupertinoApp/MacosApp (tested with all 3)
2. Override `void didChangeAccessibilityFeatures()`
3. Call `WidgetsBinding.instance.addObserver(this);` in AppWidget's `initState()`
4. Instantiate the AppWidget and pass to `runApp();`
5. Launch the app in debug mode
6. Open macOS' System Preferences -> Accessibility -> Display
7. Change "Increase contrast", "Reduce motion",



### Expected results

didChangeAccessibilityFeatures() being called

### Actual results

`didChangeAccessibilityFeatures()` is not being called

For comparison, `didChangePlatformBrightness()` works as intended however

To be noted: asking for `View.of(context).platformDispatcher.accessibilityFeatures.highContrast` even inside the brightness  callback (with the below line uncommented, so changing contrast in system preferences, then changing to dark mode to trigger callback) always returns false.

### Code sample

<details open><summary>Code sample</summary>

```dart
import 'package:flutter/foundation.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter/material.dart' as Material;

void main() {
  runApp(AppWidget());
}

class AppWidget extends StatefulWidget {
  const AppWidget({ Key? key }) : super(key: key);

  @override
  _AppWidgetState createState() => _AppWidgetState();
}

class _AppWidgetState extends State<AppWidget> with WidgetsBindingObserver {
  bool? _contrast = null;
  Brightness? _brightness = null;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);

    // get values on next frame
    WidgetsBinding.instance.addPostFrameCallback((_) {
      didChangeAccessibilityFeatures();
      didChangePlatformBrightness();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Material.MaterialApp(
      title: "Test",
      home: Material.Scaffold(
        body: Column(
          children: [
            Text("Hello, World!"),
            Text("Brightness: ${_brightness}"),
            Text("Contrast: ${_contrast}"),
          ]
        )
      )
    );
  }

  @override
  void didChangeAccessibilityFeatures() {
    super.didChangeAccessibilityFeatures();
    print("Accessibility features changed");

    setState(() {
      _contrast = View.of(context).platformDispatcher.accessibilityFeatures.highContrast;
    });
  }

  @override
  void didChangePlatformBrightness() {
    super.didChangePlatformBrightness();
    print("Platform brightness changed");

    setState(() {
      _brightness = View.of(context).platformDispatcher.platformBrightness;
      // _contrast = View.of(context).platformDispatcher.accessibilityFeatures.highContrast;
    });
  }
}
```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details open><summary>Logs</summary>

(no logs)

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.22.2, on macOS 14.4.1 23E224 darwin-arm64, locale en-US)
[✗] Android toolchain - develop for Android devices
    ✗ 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/docs/get-started/install/macos#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.

[!] Xcode - develop for iOS and macOS (Xcode 15.4)
    ✗ Unable to get list of installed Simulator runtimes.
[✓] Chrome - develop for the web
[!] Android Studio (not installed)
[✓] VS Code (version 1.91.1)
[✓] Connected device (5 available)
[✓] Network resources

! Doctor found issues in 3 categories.
```

</details>

EDIT: for context, the app doesn't seem to be responding to any of the Accessibility->Display settings changes on macOS, Smart Invert does not seem to be working with images either