Store actual Reference(s) for additional exports.

pkg/kernel/lib/import_table.dart

Index: pkg/kernel/lib/import_table.dart
diff --git a/pkg/kernel/lib/import_table.dart b/pkg/kernel/lib/import_table.dart
index 89c2998256d7015891c7e6167ba8a756b0d14334..c892e5ee5df7314ffba0a965867ca0d32ce85d48 100644
--- a/pkg/kernel/lib/import_table.dart
+++ b/pkg/kernel/lib/import_table.dart
@@ -102,6 +102,13 @@ class _ImportTableBuilder extends RecursiveVisitor {
     addLibraryImport(node.enclosingLibrary);
   }
 
+  visitLibrary(Library node) {
+    super.visitLibrary(node);
+    for (Reference exportedReference in node.additionalExports) {
+      addLibraryImport(exportedReference.node.parent);
+    }
+  }
+
   defaultMemberReference(Member node) {
     addLibraryImport(node.enclosingLibrary);
   }