[parser] Fix scopes in rewriting of for-of and destructuring assignments.

test/mjsunit/regress/regress-5648.js

Index: test/mjsunit/regress/regress-5648.js
diff --git a/test/mjsunit/regress/regress-5648.js b/test/mjsunit/regress/regress-5648.js
new file mode 100644
index 0000000000000000000000000000000000000000..840e4c1946d5a44483e3b743a2226047706558d5
--- /dev/null
+++ b/test/mjsunit/regress/regress-5648.js
@@ -0,0 +1,16 @@
+// 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.
+
+
+var iter = {}
+iter[Symbol.iterator] = () => ({
+  next: () => ({}),
+  return: () => {throw 666}
+});
+
+function* foo() {
+  for (let x of iter) {throw 42}
+}
+
+assertThrowsEquals(() => foo().next(), 42);