[es6] use correct --harmony-destructuring-assignment flag when preparsing

BUG=v8:811, v8:4636
LOG=N
R=adamk@chromium.org, yangguo@chromium.org

Review URL: https://codereview.chromium.org/1544483002

Cr-Commit-Position: refs/heads/master@{#32991}

src/parsing/parser.cc

@@ -4924,6 +4924,7 @@ PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
     SET_ALLOW(harmony_sloppy_let);
     SET_ALLOW(harmony_default_parameters);
     SET_ALLOW(harmony_destructuring_bind);
+    SET_ALLOW(harmony_destructuring_assignment);
     SET_ALLOW(strong_mode);
     SET_ALLOW(harmony_do_expressions);
     SET_ALLOW(harmony_function_name);

test/mjsunit/harmony/destructuring-assignment-lazy.js

+// 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-destructuring-assignment --harmony-destructuring-bind
+// Flags: --min-preparse-length=0
+
+function f() {
+  var a, b;
+  [ a, b ] = [1, 2];
+  assertEquals(1, a);
+  assertEquals(2, b);
+}
+
+f();