[es6] Initial support for let/const bindings in sloppy mode

src/preparser.h

 // 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.
 
 #ifndef V8_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 476 matching lines @@
   }
 
   typename Traits::Type::Factory* factory() {
     return function_state_->factory();
   }
 
   LanguageMode language_mode() { return scope_->language_mode(); }
   bool is_generator() const { return function_state_->is_generator(); }
 
   bool allow_const() {
-    return is_strict(language_mode()) || allow_legacy_const();
+    return is_strict(language_mode()) || allow_harmony_sloppy() ||
+           allow_legacy_const();
+  }
+
+  bool allow_let() {
+    return is_strict(language_mode()) || allow_harmony_sloppy();
   }
 
   // Report syntax errors.
   void ReportMessage(MessageTemplate::Template message, const char* arg = NULL,
                      ParseErrorType error_type = kSyntaxError) {
     Scanner::Location source_location = scanner()->location();
     Traits::ReportMessageAt(source_location, message, arg, error_type);
   }
 
   void ReportMessageAt(Scanner::Location location,
@@ skipping 3460 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H