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

pkg/kernel/lib/binary/limited_ast_to_binary.dart

Index: pkg/kernel/lib/binary/limited_ast_to_binary.dart
diff --git a/pkg/kernel/lib/binary/limited_ast_to_binary.dart b/pkg/kernel/lib/binary/limited_ast_to_binary.dart
index 67400c8367e27d5a19f85d196e253abf60880a29..5766f67413192dbf163a1c525e018d5f06fe82eb 100644
--- a/pkg/kernel/lib/binary/limited_ast_to_binary.dart
+++ b/pkg/kernel/lib/binary/limited_ast_to_binary.dart
@@ -108,14 +108,6 @@ class ReferencesStringIndexer extends StringIndexer {
     _handleReferencedName(node.canonicalName);
   }
 
-  @override
-  visitLibrary(Library node) {
-    for (var reference in node.additionalExports) {
-      _handleReferencedName(reference.canonicalName);
-    }
-    super.visitLibrary(node);
-  }
-
   @override
   visitLibraryDependency(LibraryDependency node) {
     _handleReferencedName(node.importedLibraryReference.canonicalName);