Ensure arrow functions can close over lexically-scoped variables

ParseArrowFunctionLiteral was erroneously checking AllowsLazyCompilation
rather than AllowsLazyParsing when deciding whether to parse lazily.
This meant that lexically-scoped variables that had no other referents
wouldn't get closed over properly.

BUG=chromium:580934, v8:4255
LOG=y

Review URL: https://codereview.chromium.org/1630823006

Cr-Commit-Position: refs/heads/master@{#33530}

src/parsing/parser-base.h

@@ -3027,7 +3027,7 @@ ParserBase<Traits>::ParseArrowFunctionLiteral(
       // Multiple statement body
       Consume(Token::LBRACE);
       bool is_lazily_parsed =
-          (mode() == PARSE_LAZILY && scope_->AllowsLazyCompilation());
+          (mode() == PARSE_LAZILY && scope_->AllowsLazyParsing());
       if (is_lazily_parsed) {
         body = this->NewStatementList(0, zone());
         this->SkipLazyFunctionBody(&materialized_literal_count,

test/mjsunit/regress/regress-crbug-580934.js

+// 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.
+//
+// Flags: --min-preparse-length=0
+
+"use strict";
+{
+  let one = () => {
+    return "example.com";
+  };
+
+  let two = () => {
+    return one();
+  };
+
+  assertEquals("example.com", two());
+}