Revert "Store actual Reference(s) for additional exports."

pkg/kernel/lib/ast.dart

Index: pkg/kernel/lib/ast.dart
diff --git a/pkg/kernel/lib/ast.dart b/pkg/kernel/lib/ast.dart
index 522b24c69752de9435cdc98552c4925fbab46902..02ca68710c70dbf81681324d97e057da5edde798 100644
--- a/pkg/kernel/lib/ast.dart
+++ b/pkg/kernel/lib/ast.dart
@@ -269,12 +269,6 @@ class Library extends NamedNode implements Comparable<Library> {
   String name;
   final List<Expression> annotations;
   final List<LibraryDependency> dependencies;
-
-  /// References to nodes exported by `export` declarations that:
-  /// - aren't ambiguous, or
-  /// - aren't hidden by local declarations.
-  final List<Reference> additionalExports = <Reference>[];
-
   @informative
   final List<LibraryPart> parts;
   final List<Typedef> typedefs;