Block scoped const variables.

src/messages.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 222 matching lines @@
       "strict_reserved_word",         ["Use of future reserved word in strict mode"],
       "strict_delete",                ["Delete of an unqualified identifier in strict mode."],
       "strict_delete_property",       ["Cannot delete property '", "%0", "' of ", "%1"],
       "strict_const",                 ["Use of const in strict mode."],
       "strict_function",              ["In strict mode code, functions can only be declared at top level or immediately within another function." ],
       "strict_read_only_property",    ["Cannot assign to read only property '", "%0", "' of ", "%1"],
       "strict_cannot_assign",         ["Cannot assign to read only '", "%0", "' in strict mode"],
       "strict_poison_pill",           ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
       "strict_caller",                ["Illegal access to a strict mode caller function."],
       "unprotected_let",              ["Illegal let declaration in unprotected statement context."],
+      "unprotected_const",            ["Illegal const declaration in unprotected statement context."],
       "cant_prevent_ext_external_array_elements", ["Cannot prevent extension of an object with external array elements"],
       "redef_external_array_element", ["Cannot redefine a property of an object with external array elements"],
     ];
     var messages = { __proto__ : null };
     var desc = new PropertyDescriptor();
     desc.setConfigurable(false);
     desc.setEnumerable(false);
     desc.setWritable(false);
     for (var i = 0; i < messagesDictionary.length; i += 2) {
       var key = messagesDictionary[i];
@@ skipping 932 matching lines @@
     throw e;
   }
 }
 
 
 InstallFunctions($Error.prototype, DONT_ENUM, ['toString', errorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Isolate::StackOverflow().
 const kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);