[js-perf-test] Add RegExp microbenchmarks

test/js-perf-test/RegExp/slow_exec.js

Index: test/js-perf-test/RegExp/slow_exec.js
diff --git a/test/js-perf-test/RegExp/slow_exec.js b/test/js-perf-test/RegExp/slow_exec.js
new file mode 100644
index 0000000000000000000000000000000000000000..bb1948366c50e150fcb0348aa9a1866370d42ab4
--- /dev/null
+++ b/test/js-perf-test/RegExp/slow_exec.js
@@ -0,0 +1,8 @@
+// Copyright 2016 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.
+
+load("base.js");
+load("base_exec.js");
+
+createSlowBenchmarkSuite("Exec");