Some re-exported symbols have the wrong library links #1345
Description
For example MaskFilter:
https://docs.flutter.io/flutter/dart-ui/MaskFilter-class.html
Has the "Widgets" library link in its header, but it's defined in dart:ui (and the url for it is correct!)
I would expect it to look more like other dart:ui defined classes and have a dart:ui library link which matches its url, like Window does:
Originally reported as flutter/flutter#8239.
Likely just a small missing part of #1158.