Bugfix: Add platformBrightness to TestWindow. (#27569)

* Bugfix: Add platformBrightness to TestWindow.

* Manual engine roll:

cc27cafb8 Implemented Dark Mode for Android (#25525) ([flutter/engine#7488](https://github.com/flutter/engine/pull/7488))
9c05cbcfb Roll src/third_party/dart b53dceadaa..5823be65af (5 commits) 5823be65af [vm/compiler] Continued graph checker development (reland) 8231cdb7a3 [gardening] Update status for issue 35854 db7f848632 [vm] Remove dead BigInt code. 35ab1755f4 Support more type propagation for code-as-ui features 569ee07f91 [vm] Cleanup class finalization checks
ec5e6f6ef Ensure dart2js and kernel worker snapshots are copied out of gen dir ([flutter/engine#7692](https://github.com/flutter/engine/pull/7692))
8b5fa65c4 Roll src/third_party/skia 50ea3c06b80f..2d35a1c87553 (6 commits) ([flutter/engine#7693](https://github.com/flutter/engine/pull/7693))

bin/internal/engine.version

-93aa035dd46999353d8f7fe4be61e6599c794b4b
+cc27cafb840f6fd57b86a36a3e7ed5461575f10a

packages/flutter_test/lib/src/window.dart

@@ -151,6 +151,24 @@ class TestWindow implements Window {
     _textScaleFactorTestValue = null;
   }
 
+  @override
+  Brightness get platformBrightness => _platformBrightnessTestValue ?? _window.platformBrightness;
+  Brightness _platformBrightnessTestValue;
+  @override
+  VoidCallback get onPlatformBrightnessChanged => _window.onPlatformBrightnessChanged;
+  @override
+  set onPlatformBrightnessChanged(VoidCallback callback) {
+    _window.onPlatformBrightnessChanged =callback;
+  }
+  /// Hides the real text scale factor and reports the given [platformBrightnessTestValue] instead.
+  set platformBrightnessTestValue(Brightness platformBrightnessTestValue) {
+    _platformBrightnessTestValue = platformBrightnessTestValue;
+  }
+  /// Deletes any existing test platform brightness and returns to using the real platform brightness.
+  void clearPlatformBrightnessTestValue() {
+    _platformBrightnessTestValue = null;
+  }
+
   @override
   bool get alwaysUse24HourFormat => _alwaysUse24HourFormatTestValue ?? _window.alwaysUse24HourFormat;
   bool _alwaysUse24HourFormatTestValue;
@@ -292,6 +310,7 @@ class TestWindow implements Window {
     clearAlwaysUse24HourTestValue();
     clearDefaultRouteNameTestValue();
     clearDevicePixelRatioTestValue();
+    clearPlatformBrightnessTestValue();
     clearLocaleTestValue();
     clearLocalesTestValue();
     clearPaddingTestValue();

packages/flutter_test/test/window_test.dart

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:ui' as ui show window;
-import 'dart:ui' show Size, Locale, WindowPadding, AccessibilityFeatures;
+import 'dart:ui' show Size, Locale, WindowPadding, AccessibilityFeatures, Brightness;
 
 import 'package:flutter/widgets.dart' show WidgetsBinding;
 import 'package:flutter_test/flutter_test.dart';
@@ -164,6 +164,20 @@ void main() {
     );
   });
 
+  testWidgets('TestWindow can fake platform brightness', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<Brightness>(
+      tester: tester,
+      realValue: Brightness.light,
+      fakeValue: Brightness.dark,
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.platformBrightness;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, Brightness fakeValue) {
+        binding.window.platformBrightnessTestValue = fakeValue;
+      }
+    );
+  });
+
   testWidgets('TestWindow can clear out fake properties all at once', (WidgetTester tester) {
     final double originalDevicePixelRatio = ui.window.devicePixelRatio;
     final double originalTextScaleFactor = ui.window.textScaleFactor;