anchor.diff:      return element;
     }
   
  -  /// Create an element for the given widget and add it as a child of this element in the given slot.
  +  /// Create an element for the given widget and add it as a child of this
  +  /// element in the given slot.
     ///
     /// This method is typically called by [updateChild] but can be called
     /// directly by subclasses that need finer-grained control over creating
  
positive.code: /// painting, and hit testing.
  ///
  /// Contrast with [ComponentElement].
  abstract class RenderObjectElement extends BuildableElement {
    /// Creates an element that uses the given widget as its configuration.
    RenderObjectElement(RenderObjectWidget widget) : super(widget);
  
negative.code:   @protected
    void detachChild(Element child);
  
    /// Update the given child with the given new configuration.
    ///
    /// This method is the core of the widgets system.
    ///
    /// It is called each time we are to add, update, or remove a child based on
    /// an updated configuration.
    ///
    /// If the `child` is null, and the `newWidget` is not null, then we have a new
    /// child for which we need to create an [Element], configured with `newWidget`.
    ///
    /// If the `newWidget` is null, and the `child` is not null, then we need to
    /// remove it because it no longer has a configuration.
    ///
    /// If neither are null, then we need to update the `child`'s configuration to
    /// be the new configuration given by `newWidget`. If `newWidget` can be given
    /// to the existing child (as determined by [Widget.canUpdate]), then it is so
    /// given. Otherwise, the old child needs to be disposed and a new child
    /// created for the new configuration.
    ///
    /// If both are null, then we don't have a child and won't have a child, so we
    /// do nothing.
    ///
    /// The [updateChild] method returns the new child, if it had to create one,
    /// or the child that was passed in, if it just had to update the child, or
    /// null, if it removed the child and did not replace it.
    @protected
  