anchor.diff:      if (userCode != null) {
         Set<Uri> uris = new Set<Uri>.from(userCode.loader.builders.keys);
         uris.removeAll(dillLoadedData.loader.builders.keys);
  +      if (previousSourceBuilders != null) {
  +        for(Library library in previousSourceBuilders) {
  +          uris.add(library.importUri);
  +        }
  +      }
         invalidatedUris.addAll(uris);
       }
     }
  
positive.code:       new Uri(scheme: "org-dartlang-debug", path: "synthetic_debug_expression");
  
    KernelTarget userCode;
  
    IncrementalCompiler.fromComponent(
        this.context, this.componentToInitializeFrom,
  
negative.code: 
    /// Convert every SourceLibraryBuilder to a DillLibraryBuilder.
    /// As we always do this, this will only be the new ones.
    ///
    /// Returns the set of Libraries that now has new (dill) builders.
    Future<Set<Library>> convertSourceLibraryBuildersToDill() async {
      bool changed = false;
      Set<Library> newDillLibraryBuilders = new Set<Library>();
      userBuilders ??= <Uri, LibraryBuilder>{};
      for (MapEntry<Uri, LibraryBuilder> entry
          in userCode.loader.builders.entries) {
  