Update dart:io to convert strings between UTF8 and current code page

runtime/bin/utils.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_UTILS_H_
 #define BIN_UTILS_H_
 
 #include <stdlib.h>
 #include <string.h>
 
@@ skipping 34 matching lines @@
     }
   }
 
   SubSystem sub_system_;
   int code_;
   char* message_;
 
   DISALLOW_COPY_AND_ASSIGN(OSError);
 };
 
+class StringUtils {
+ public:
+  // The following methods convert the argument if needed.  The
+  // conversions are only needed on Windows. If the methods returns a
+  // pointer that is different from the input pointer the returned
+  // pointer is allocated with malloc and should be freed using free.
+  static const char* SystemStringToUtf8(const char* str);
+  static char* SystemStringToUtf8(char* str);
+  static const char* Utf8ToSystemString(const char* utf8);
+  static char* Utf8ToSystemString(char* utf8);
+};
+
 #endif  // BIN_UTILS_H_