dart:io | Fix File.rename on Windows to overwrite an existing target.

runtime/bin/file_win.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 "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/file.h"
 
 #include <fcntl.h>  // NOLINT
@@ skipping 273 matching lines @@
   free(const_cast<wchar_t*>(system_name));
   return result;
 }
 
 
 bool File::Rename(const char* old_path, const char* new_path) {
   File::Type type = GetType(old_path, false);
   if (type == kIsFile) {
     const wchar_t* system_old_path = StringUtils::Utf8ToWide(old_path);
     const wchar_t* system_new_path = StringUtils::Utf8ToWide(new_path);
-    DWORD flags = MOVEFILE_WRITE_THROUGH;
+    DWORD flags = MOVEFILE_WRITE_THROUGH | MOVEFILE_REPLACE_EXISTING;
     int move_status =
         MoveFileExW(system_old_path, system_new_path, flags);
     free(const_cast<wchar_t*>(system_old_path));
     free(const_cast<wchar_t*>(system_new_path));
     return (move_status != 0);
   } else {
     SetLastError(ERROR_FILE_NOT_FOUND);
   }
   return false;
 }
 
 
 bool File::RenameLink(const char* old_path, const char* new_path) {
   File::Type type = GetType(old_path, false);
   if (type == kIsLink) {
     const wchar_t* system_old_path = StringUtils::Utf8ToWide(old_path);
     const wchar_t* system_new_path = StringUtils::Utf8ToWide(new_path);
-    DWORD flags = MOVEFILE_WRITE_THROUGH;
+    DWORD flags = MOVEFILE_WRITE_THROUGH | MOVEFILE_REPLACE_EXISTING;
     int move_status =
         MoveFileExW(system_old_path, system_new_path, flags);
     free(const_cast<wchar_t*>(system_old_path));
     free(const_cast<wchar_t*>(system_new_path));
     return (move_status != 0);
   } else {
     SetLastError(ERROR_FILE_NOT_FOUND);
   }
   return false;
 }
@@ skipping 283 matching lines @@
     return kIdentical;
   } else {
     return kDifferent;
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)