Serialize exports scopes.

pkg/front_end/testcases/export_test.dart.direct.expect

Index: pkg/front_end/testcases/export_test.dart.direct.expect
diff --git a/pkg/front_end/testcases/export_test.dart.direct.expect b/pkg/front_end/testcases/export_test.dart.direct.expect
new file mode 100644
index 0000000000000000000000000000000000000000..6402fff78fa1a7f6f9f41e88b75ba343a681c794
--- /dev/null
+++ b/pkg/front_end/testcases/export_test.dart.direct.expect
@@ -0,0 +1,9 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:developer" as dev;
+
+static const field dynamic _exports# = "[[\"dart:core\",\"print\"]]" /* from null */;
+static method main() → dynamic {
+  core::print(dev::UserTag);
+}