Don't pre-initialise block contexts with holes

test/mjsunit/harmony/regress/regress-crbug-571149.js

Index: test/mjsunit/harmony/regress/regress-crbug-571149.js
diff --git a/test/mjsunit/harmony/regress/regress-crbug-571149.js b/test/mjsunit/harmony/regress/regress-crbug-571149.js
new file mode 100644
index 0000000000000000000000000000000000000000..b3325b7fdf148c9196e5fb9b112d24ab2e59c750
--- /dev/null
+++ b/test/mjsunit/harmony/regress/regress-crbug-571149.js
@@ -0,0 +1,19 @@
+// 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.
+
+
+(function(a = 0){
+  var x;  // allocated in a var block, due to use of default parameter
+  (function() { return !x })();
+})();
+
+(function({a}){
+  var x;  // allocated in a var block, due to use of parameter destructuring
+  (function() { return !x })();
+})({});
+
+(function(...a){
+  var x;  // allocated in a var block, due to use of rest parameter
+  (function() { return !x })();
+})();