anchor.diff:    /// when the device is rotated or when the application is resized (e.g. when
     /// showing applications side-by-side on Android).
     ///
  -  /// The framework invokes this callback in the same zone in which the
  -  /// callback was set.
  +  /// The engine invokes this callback in the same zone in which the callback
  +  /// was set.
  +  ///
  +  /// The framework registers with this callback and updates the layout
  +  /// appropriately.
  +  ///
  +  /// See also:
  +  ///
  +  ///  * [WidgetsBindingObserver], for a mechanism at the widgets layer to
  +  ///    register for notifications when this is called.
  +  ///  * [MediaQuery.of], a simpler mechanism for the same.
     VoidCallback get onMetricsChanged => _onMetricsChanged;
     VoidCallback _onMetricsChanged;
     Zone _onMetricsChangedZone;
  
positive.code:   /// The Flutter framework operates in logical pixels, so it is rarely
    /// necessary to directly deal with this property.
    ///
    /// See also:
    ///
    ///  * [WidgetsBindingObserver], for a mechanism at the widgets layer to
  
negative.code:   /// which the application can render, but over which the operating system
    /// will likely place system UI, such as the keyboard, that fully obscures
    /// any content.
    ///
    /// When this changes, [onMetricsChanged] is called.
    ///
    /// See also:
    ///
  