Don't treat function parameters as let-bound variables in Harmony mode.

src/parser.cc

 // Copyright 2012 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 4030 matching lines @@
         name_loc = scanner().location();
       }
       if (!dupe_loc.IsValid() && top_scope_->IsDeclared(param_name)) {
         has_duplicate_parameters = true;
         dupe_loc = scanner().location();
       }
       if (!reserved_loc.IsValid() && is_strict_reserved) {
         reserved_loc = scanner().location();
       }
 
-      top_scope_->DeclareParameter(param_name, is_extended_mode() ? LET : VAR);
+      top_scope_->DeclareParameter(param_name, VAR);
       num_parameters++;
       if (num_parameters > kMaxNumFunctionParameters) {
         ReportMessageAt(scanner().location(), "too_many_parameters",
                         Vector<const char*>::empty());
         *ok = false;
         return NULL;
       }
       done = (peek() == Token::RPAREN);
       if (!done) Expect(Token::COMMA, CHECK_OK);
     }
@@ skipping 1549 matching lines @@
       ASSERT(info->isolate()->has_pending_exception());
     } else {
       result = parser.ParseProgram(info);
     }
   }
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal