anchor.diff:  
   /// A circle that represents a user.
   ///
  -/// Typicially used with a user's profile image, or, in the absence of
  +/// Typically used with a user's profile image, or, in the absence of
   /// such an image, the user's initials. A given user's initials should
   /// always be paired with the same background color, for consistency.
   ///
  +/// If the avatar is to have an image, the image should be specified in the
  +/// [backgroundImage] property:
  +///
  +/// ```dart
  +/// new CircleAvatar(
  +///   backgroundImage: new NetworkImage(userAvatarUrl),
  +/// )
  +/// ```
  +///
  +/// The image will be cropped to have a circle shape.
  +///
  +/// If the avatar is to just have the user's initials, they are typically
  +/// provided using a [Text] widget as the [child] and a [backgroundColor]:
  +///
  +/// ```dart
  +/// new CircleAvatar(
  +///   backgroundColor: Colors.brown[800],
  +///   child: new Text('AH'),
  +/// );
  +/// ```
  +///
   /// See also:
   ///
  -///  * [Chip]
  -///  * [ListItem]
  +///  * [Chip], for representing users or concepts in long form.
  +///  * [ListItem], which combines an icon (such as a [CircleAvatar]) with some
  +///    text in a horizontal row.
   ///  * <https://material.google.com/components/chips.html#chips-contact-chips>
   class CircleAvatar extends StatelessWidget {
     /// Creates a circle that represents a user.
  
positive.code:         backgroundImage: backgroundImage != null ? new BackgroundImage(
            image: backgroundImage
          ) : null,
          shape: BoxShape.circle
        ),
        child: new Center(
          child: new DefaultTextStyle(
            style: theme.primaryTextTheme.title,
            child: child
          )
        )
      );
    }
  }
  
negative.code: 
    /// The background image of the circle. Changing the background
    /// image will cause the avatar to animate to the new image.
    ///
    /// If the [CircleAvatar] is to have the user's initials, use [child] instead.
    final ImageProvider backgroundImage;
  
    /// The size of the avatar. Changing the radius will cause the
    /// avatar to animate to the new size.
    ///
    /// Defaults to 20 logical pixels.
    final double radius;
  
    @override
    Widget build(BuildContext context) {
      final ThemeData theme = Theme.of(context);
      final Color color = backgroundColor ?? theme.primaryColor;
      return new AnimatedContainer(
        width: radius * 2.0,
        height: radius * 2.0,
  