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

src/rewriter.cc

Index: src/rewriter.cc
diff --git a/src/rewriter.cc b/src/rewriter.cc
index ee08d885f602f2d110e60a540cf7a0e4281ce241..c901653a2ba3c6aff53a4e13fb463f0a667c7ddf 100644
--- a/src/rewriter.cc
+++ b/src/rewriter.cc
@@ -83,7 +83,7 @@ void Processor::VisitBlock(Block* node) {
   // 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());
 }