Regression test for JSRegExp literals sharing.

test/mjsunit/regress/regress-crbug-548580.js

Index: test/mjsunit/regress/regress-crbug-548580.js
diff --git a/test/mjsunit/regress/regress-crbug-548580.js b/test/mjsunit/regress/regress-crbug-548580.js
new file mode 100644
index 0000000000000000000000000000000000000000..4a2f5e152ffc42a2f87ad6c1f089927807ea5a1d
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-548580.js
@@ -0,0 +1,17 @@
+// Copyright 2015 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.
+
+// Flags: --harmony-regexps
+
+function store(v) {
+  var re = /(?=[d#.])/;
+  re.a = v;
+  return re;
+}
+
+var re1 = store(undefined);
+var re2 = store(42);
+
+assertEquals(re1.a, undefined);
+assertEquals(re2.a, 42);