anchor.diff:          ServiceExtensionButton(debugAllowBanner).button,
         ]),
       div(c: 'btn-group nowrap margin-left')
  -      ..add(ServiceExtensionSelector(togglePlatformMode).selector)
  +      ..add(TogglePlatformSelector().selector)
     ];
   }
   
  
positive.code: 
  import '../globals.dart';
  import '../service_extensions.dart';
  import '../service_registrations.dart';
  import '../utils.dart';
  import 'analytics.dart' as ga;
  
negative.code:     _selectedValue = selector.value;
    }
  
    void addOptions() {
      extensionDescription.displayValues.forEach(selector.option);
    }
  
    void updateState() {
      // Select option whose state is already enabled.
      serviceManager.serviceExtensionManager
          .getServiceExtensionState(extensionDescription.extension, (state) {
        updateSelection(state);
      });
    }
  
    void updateSelection(ServiceExtensionState state) {
      if (state.value != null) {
        final selectedIndex = extensionDescription.values.indexOf(state.value);
        selector.selectedIndex = selectedIndex;
        _selectedValue = extensionDescription.displayValues[selectedIndex];
      }
    }
  }
  
  class TogglePlatformSelector extends ServiceExtensionSelector {
    TogglePlatformSelector() : super(togglePlatformMode);
  
    static const fuchsia = 'Fuchsia';
  
    @override
    void addOptions() {
      extensionDescription.displayValues
          .where((displayValue) => !displayValue.contains(fuchsia))
          .forEach(selector.option);
    }
  
    @override
    void updateState() {
      // Select option whose state is already enabled.
      serviceManager.serviceExtensionManager
          .getServiceExtensionState(extensionDescription.extension, (state) {
        if (state.value == fuchsia.toLowerCase()) {
          selector.option(extensionDescription.displayValues
              .firstWhere((displayValue) => displayValue.contains(fuchsia)));
        }
        updateSelection(state);
      });
    }
  }
  