[es6] Don't eliminate tail calls from for-in and for-of bodies.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index ea5072e27d7b5c071b0a91ee86db353b3d1e3a31..3549cca365e8f77393a38ca0c3aea39daed8e112 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -3555,6 +3555,8 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
             factory()->NewBlock(NULL, 3, false, RelocInfo::kNoPosition);
 
         {
+          DontCollectExpressionsInTailPositionScope no_tail_calls(
+              function_state_);
           BlockState block_state(&scope_, body_scope);
 
           Statement* body = ParseScopedStatement(NULL, true, CHECK_OK);