Flush UserSettings to window (#6850)

lib/ui/hooks.dart

@@ -68,6 +68,9 @@ void _updateLocales(List<String> locales) {
 @pragma('vm:entry-point')
 void _updateUserSettingsData(String jsonData) {
   final Map<String, dynamic> data = json.decode(jsonData);
+  if (data.isEmpty) {
+    return;
+  }
   _updateTextScaleFactor(data['textScaleFactor'].toDouble());
   _updateAlwaysUse24HourFormat(data['alwaysUse24HourFormat']);
 }

runtime/runtime_controller.cc

@@ -128,7 +128,8 @@ bool RuntimeController::FlushRuntimeStateToIsolate() {
   return SetViewportMetrics(window_data_.viewport_metrics) &&
          SetLocales(window_data_.locale_data) &&
          SetSemanticsEnabled(window_data_.semantics_enabled) &&
-         SetAccessibilityFeatures(window_data_.accessibility_feature_flags_);
+         SetAccessibilityFeatures(window_data_.accessibility_feature_flags_) &&
+         SetUserSettingsData(window_data_.user_settings_data);
 }
 
 bool RuntimeController::SetViewportMetrics(const ViewportMetrics& metrics) {

testing/dart/window_hooks_integration_test.dart

@@ -67,6 +67,12 @@ void main() {
       window.onTextScaleFactorChanged = originalOnTextScaleFactorChanged;
     });
 
+    test('updateUserSettings can handle an empty object', () {
+      // this should now throw.
+      _updateUserSettingsData('{}');
+      expect(true, equals(true));
+    });
+
     test('onMetricsChanged preserves callback zone', () {
       Zone innerZone;
       Zone runZone;