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

src/parsing/parser.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/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 3537 matching lines @@
 
         Expect(Token::RPAREN, CHECK_OK);
 
         Scope* body_scope = NewScope(scope_, BLOCK_SCOPE);
         body_scope->set_start_position(scanner()->location().beg_pos);
 
         Block* body_block =
             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);
 
           auto each_initialization_block =
               factory()->NewBlock(nullptr, 1, true, RelocInfo::kNoPosition);
           {
             auto descriptor = parsing_result.descriptor;
             descriptor.declaration_pos = RelocInfo::kNoPosition;
             descriptor.initialization_pos = RelocInfo::kNoPosition;
@@ skipping 3223 matching lines @@
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
 
 }  // namespace internal
 }  // namespace v8