Store actual Reference(s) for additional exports.

pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
index 99fc60f3ec0ecb65c98690afca5e8c081ff1133c..75532f6c17c868fbcdd31c4d7ef46bc1fb485e0b 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
@@ -4,8 +4,6 @@
 
 library fasta.kernel_library_builder;
 
-import 'dart:convert' show JSON;
-
 import 'package:front_end/src/fasta/combinator.dart' as fasta;
 import 'package:front_end/src/fasta/export.dart';
 import 'package:front_end/src/fasta/import.dart';
@@ -784,10 +782,7 @@ class KernelLibraryBuilder
     library.procedures.sort(compareProcedures);
 
     if (additionalExports != null) {
-      library.addMember(new Field(new Name("_exports#", library),
-          initializer: new StringLiteral(JSON.encode(additionalExports)),
-          isStatic: true,
-          isConst: true));
+      library.additionalExports.addAll(additionalExports);
     }
 
     return library;