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 5766f67413192dbf163a1c525e018d5f06fe82eb..67400c8367e27d5a19f85d196e253abf60880a29 100644
--- a/pkg/kernel/lib/binary/limited_ast_to_binary.dart
+++ b/pkg/kernel/lib/binary/limited_ast_to_binary.dart
@@ -108,6 +108,14 @@ 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);