Fix Windows build.

runtime/bin/dartutils.cc

 // 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.
 
 #include "bin/dartutils.h"
 
 #include "bin/crypto.h"
 #include "bin/directory.h"
 #include "bin/extensions.h"
 #include "bin/file.h"
@@ skipping 220 matching lines @@
     return colon + 1;
   }
 }
 
 
 char* DartUtils::DirName(const char* url) {
   const char* slash = strrchr(url, File::PathSeparator()[0]);
   if (slash == NULL) {
     return strdup(url);
   } else {
-    return strndup(url, slash - url + 1);
+    return StringUtils::StrNDup(url, slash - url + 1);
   }
 }
 
 
 void* DartUtils::OpenFile(const char* name, bool write) {
   File* file = File::Open(name, write ? File::kWriteTruncate : File::kRead);
   return reinterpret_cast<void*>(file);
 }
 
 
@@ skipping 925 matching lines @@
       new CObjectString(CObject::NewString(os_error->message()));
   CObjectArray* result = new CObjectArray(CObject::NewArray(3));
   result->SetAt(0, new CObjectInt32(CObject::NewInt32(kOSError)));
   result->SetAt(1, new CObjectInt32(CObject::NewInt32(os_error->code())));
   result->SetAt(2, error_message);
   return result;
 }
 
 }  // namespace bin
 }  // namespace dart