anchor.diff:    }
   
     /// Appends the given layer to the recording, and calls the `painter` callback
  -  /// with that layer, providing the `childPaintBounds` as the paint bounds of
  -  /// the child. Canvas recording commands are not guaranteed to be stored
  -  /// outside of the paint bounds.
  +  /// with that layer, providing the `childPaintBounds` as the estimated paint
  +  /// bounds of the child.  The `childPaintBounds` can be used for debugging but
  +  /// have no effect on painting.
     ///
     /// The given layer must be an unattached orphan. (Providing a newly created
     /// object, rather than reusing an existing layer, satisfies that
  
positive.code:   }
  
    @override
    String toString() => '$runtimeType#$hashCode(layer: $_containerLayer, canvas bounds: $canvasBounds)';
  }
  
  /// An abstract set of layout constraints.
  
negative.code:   /// The current canvas can change whenever you paint a child using this
    /// context, which means it's fragile to hold a reference to the canvas
    /// returned by this getter.
    Canvas get canvas {
      if (_canvas == null)
        _startRecording();
  