Undo change that converted exit code 255 to -1.

runtime/bin/process_win.cc

 // Copyright (c) 2011, 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 <process.h>
 
 #include "bin/builtin.h"
 #include "bin/globals.h"
 #include "bin/process.h"
 #include "bin/eventhandler.h"
@@ skipping 193 matching lines @@
 static unsigned int __stdcall TerminationWaitThread(void* args) {
   ProcessInfo* process = reinterpret_cast<ProcessInfo*>(args);
   WaitForSingleObject(process->process_handle(), INFINITE);
   int exit_code;
   BOOL ok = GetExitCodeProcess(process->process_handle(),
                                reinterpret_cast<DWORD*>(&exit_code));
   if (!ok) {
     fprintf(stderr, "GetExitCodeProcess failed %d\n", GetLastError());
   }
   int negative = 0;
-  if (exit_code == 255) {
-    exit_code = 1;
-    negative = 1;
-  }
   if (exit_code < 0) {
     exit_code = abs(exit_code);
     negative = 1;
   }
   int message[3] = { process->pid(), exit_code, negative };
   DWORD written;
   ok = WriteFile(
       process->exit_pipe(), message, sizeof(message), &written, NULL);
   if (!ok || written != sizeof(message)) {
     fprintf(stderr, "WriteFile failed %d\n", GetLastError());
@@ skipping 180 matching lines @@
       return false;
     }
   }
   return true;
 }
 
 
 void Process::Exit(intptr_t id) {
   RemoveProcess(id);
 }