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

runtime/bin/utils.h

Index: runtime/bin/utils.h
diff --git a/runtime/bin/utils.h b/runtime/bin/utils.h
index 7c050a424ae403f58648b4a934b4166f4bbae2b5..f147778ebd8f92a440bf170f79238177874fd2b7 100644
--- a/runtime/bin/utils.h
+++ b/runtime/bin/utils.h
@@ -52,4 +52,16 @@ class OSError {
   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_