anchor.diff:      );
     }
   
  -  /// Specifies the set of overlays visible on the embedder when the
  -  /// application is running. The embedder may choose to ignore unsupported
  -  /// overlays
  +  /// Specifies the set of system overlays to have visible when the application
  +  /// is running.
     ///
  -  /// Arguments:
  +  /// The `overlays` argument is a list of [SystemUiOverlay] enum values
  +  /// denoting the overlays to show.
     ///
  -  ///  * [overlaysMask]: A mask of [SystemUiOverlay] enum values that denotes
  -  ///    the overlays to show.
  -  ///
  -  /// Platform Specific Notes:
  -  ///
  -  ///   If the overlay is unsupported on the platform, enabling or disabling
  -  ///   that overlay is a no-op and always return true.
  +  /// If a particular overlay is unsupported on the platform, enabling or
  +  /// disabling that overlay will be ignored.
     static Future<Null> setEnabledSystemUIOverlays(List<SystemUiOverlay> overlays) async {
       await PlatformMessages.invokeMethod(
         _kChannelName,
  
positive.code:   return result;
  }
  
  /// Controls specific aspects of the embedder interface.
  class SystemChrome {
    SystemChrome._();
  
    /// Specifies the set of orientations the application interface can
    /// be displayed in.
    ///
    /// Arguments:
    ///
    ///  * [orientation]: A list of [DeviceOrientation] enum values. The empty
    ///    list is synonymous with having all options enabled.
    static Future<Null> setPreferredOrientations(List<DeviceOrientation> orientations) async {
      await PlatformMessages.invokeMethod(
        _kChannelName,
  
negative.code: 
  /// Specifies a particular device orientation.
  ///
  /// To determine which values correspond to which orientations, first position
  /// the device in its default orientation (this is the orientation that the
  /// system first uses for its boot logo, or the orientation in which the
  /// hardware logos or markings are upright, or the orientation in which the
  /// cameras are at the top). If this is a portrait orientation, then this is
  /// [portraitUp]. Otherwise, it's [landscapeLeft]. As you rotate the device by
  /// 90 degrees in a counter-clockwise direction around the axis that pierces the
  /// screen, you step through each value in this enum in the order given.
  ///
  /// For a device with a landscape default orientation, the orientation obtained
  /// by rotating the device 90 degrees clockwise from its default orientation is
  /// [portraitUp].
  ///
  /// Used by [SystemChrome.setPreferredOrientations].
  enum DeviceOrientation {
    /// If the device shows its boot logo in portrait, then the boot logo is shown
    /// in [portraitUp]. Otherwise, the device shows its boot logo in landscape
  