[dart:io][windows] Make unicode characters display correctly.

runtime/bin/utils_win.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 RUNTIME_BIN_UTILS_WIN_H_
 #define RUNTIME_BIN_UTILS_WIN_H_
 
 #include "platform/globals.h"
 
 namespace dart {
@@ skipping 59 matching lines @@
 class Utf8ToWideScope {
  public:
   explicit Utf8ToWideScope(const char* utf8) {
     int wide_len = MultiByteToWideChar(CP_UTF8, 0, utf8, -1, NULL, 0);
     wchar_t* wide = new wchar_t[wide_len];
     MultiByteToWideChar(CP_UTF8, 0, utf8, -1, wide, wide_len);
     length_ = wide_len;
     wide_ = wide;
   }
 
+  Utf8ToWideScope(const char* utf8, intptr_t length) {
+    int wide_len = MultiByteToWideChar(CP_UTF8, 0, utf8, length, NULL, 0);
+    wchar_t* wide = new wchar_t[wide_len];
+    MultiByteToWideChar(CP_UTF8, 0, utf8, length, wide, wide_len);
+    length_ = wide_len;
+    wide_ = wide;
+  }
+
   ~Utf8ToWideScope() { delete[] wide_; }
 
   wchar_t* wide() const { return wide_; }
   intptr_t length() const { return length_; }
+  intptr_t size_in_bytes() const { return length_ * sizeof(*wide_); }
 
  private:
   intptr_t length_;
   wchar_t* wide_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Utf8ToWideScope);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // RUNTIME_BIN_UTILS_WIN_H_