Don't re-export hidden members.

pkg/front_end/lib/src/fasta/source/source_loader.dart

Index: pkg/front_end/lib/src/fasta/source/source_loader.dart
diff --git a/pkg/front_end/lib/src/fasta/source/source_loader.dart b/pkg/front_end/lib/src/fasta/source/source_loader.dart
index a5f5ed2a68d796239de913ebf768805e61cc8357..aa70b336fef059f1b6e05290b9214ea9a1accd32 100644
--- a/pkg/front_end/lib/src/fasta/source/source_loader.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_loader.dart
@@ -231,9 +231,8 @@ class SourceLoader<L> extends Loader<L> {
       wasChanged = false;
       for (SourceLibraryBuilder exported in both) {
         for (Export export in exported.exporters) {
-          SourceLibraryBuilder exporter = export.exporter;
           exported.exportScope.forEach((String name, Builder member) {
-            if (exporter.addToExportScope(name, member)) {
+            if (export.addToExportScope(name, member)) {
               wasChanged = true;
             }
           });