[es6] Fix completion values of for loops with lexical variables

src/rewriter.cc

 // Copyright 2012 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.
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/parser.h"
 #include "src/rewriter.h"
 #include "src/scopes.h"
@@ skipping 65 matching lines @@
 
 void Processor::VisitBlock(Block* node) {
   // An initializer block is the rewritten form of a variable declaration
   // with initialization expressions. The initializer block contains the
   // list of assignments corresponding to the initialization expressions.
   // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
   // a variable declaration with initialization expression is 'undefined'
   // with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
   // returns 'undefined'. To obtain the same behavior with v8, we need
   // to prevent rewriting in that case.
-  if (!node->is_initializer_block()) Process(node->statements());
+  if (!node->ignore_completion_value()) Process(node->statements());
 }
 
 
 void Processor::VisitExpressionStatement(ExpressionStatement* node) {
   // Rewrite : <x>; -> .result = <x>;
   if (!is_set_ && !node->expression()->IsThrow()) {
     node->set_expression(SetResult(node->expression()));
     if (!in_try_) is_set_ = true;
   }
 }
@@ skipping 146 matching lines @@
       body->Add(result_statement, info->zone());
     }
   }
 
   return true;
 }
 
 
 }  // namespace internal
 }  // namespace v8