Add test case for SparseJoin misbehavior with getters

test/mjsunit/bugs/bug-3621.js

Index: test/mjsunit/bugs/bug-3621.js
diff --git a/test/mjsunit/bugs/bug-3621.js b/test/mjsunit/bugs/bug-3621.js
new file mode 100644
index 0000000000000000000000000000000000000000..16ddde16961cd0cbd42d0d64118a85a0241ee9c2
--- /dev/null
+++ b/test/mjsunit/bugs/bug-3621.js
@@ -0,0 +1,11 @@
+// Copyright 2014 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.
+
+var a = [];
+var endIndex = 0xffff;
+a[endIndex] = 3;
+Object.defineProperty(a, 0, { get: function() { this[1] = 2; return 1; } });
+assertEquals('123', a.join(''));
+delete a[1];  // reset the array
+assertEquals('1,2,', a.join().slice(0, 4));