Pass legacy const runtime flag to preparser appropriately

test/message/const-decl-no-init-sloppy.js

Index: test/message/const-decl-no-init-sloppy.js
diff --git a/test/message/for-in-loop-initializers-destructuring.js b/test/message/const-decl-no-init-sloppy.js
similarity index 77%
copy from test/message/for-in-loop-initializers-destructuring.js
copy to test/message/const-decl-no-init-sloppy.js
index 9bbfd8d71f822b3dfb1fe922bd29e6b7e7174abd..93c98b2846f1ca43b9c4041403cefbdebd660f59 100644
--- a/test/message/for-in-loop-initializers-destructuring.js
+++ b/test/message/const-decl-no-init-sloppy.js
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-//
+// Flags: --no-legacy-const --harmony-sloppy
 
 function f() {
-  for (var [x, y] = {} in {});
+  const a;
 }