ImageSpan not update on Hot reload

[2dxgujun]

I figure out that when you trigger a Hot reload, _RichTextWrapper will invoke updateRenderObject and it will call RenderParagraph's text setter to set a new TextSpan which call TextSpan.compareTo to determine whether to accept the new TextSpan or drop it.

Since our ImageSpan is inherited from TextSpan, and we should override the compareTo method to aware the changes of these properties in ImageSpan class.

Here is my patch code, and it works.

@override
RenderComparison compareTo(covariant ImageSpan other) {
  RenderComparison comparison = super.compareTo(other);
  if (other.imageProvider != imageProvider ||
      other.imageWidth != imageWidth ||
      other.imageHeight != imageHeight ||
      other.margin != margin) {
    comparison = RenderComparison.layout;
  }
  return comparison;
}