[modules] Add a simple micro-benchmark for import/export accesses.

test/js-perf-test/Modules/basic-export.js

Index: test/js-perf-test/Modules/basic-export.js
diff --git a/test/js-perf-test/Modules/basic-export.js b/test/js-perf-test/Modules/basic-export.js
new file mode 100644
index 0000000000000000000000000000000000000000..3b889747afaf733ff10fe5a91e25b81e2dfa728b
--- /dev/null
+++ b/test/js-perf-test/Modules/basic-export.js
@@ -0,0 +1,7 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export let value = 0;
+for (let i = 0; i < iterations; ++i) ++value;
+if (value != iterations) throw value;