Reapply "Add a sleep function to dart:io"

runtime/bin/utils.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 BIN_UTILS_H_
 #define BIN_UTILS_H_
 
 #include <stdlib.h>
 #include <string.h>
 
@@ skipping 64 matching lines @@
   // If GetUnicodeArgv returns a pointer that pointer has to be
   // deallocated with a call to FreeUnicodeArgv.
   static wchar_t** GetUnicodeArgv(int* argc);
   static void FreeUnicodeArgv(wchar_t** argv);
 };
 
 class TimerUtils {
  public:
   static int64_t GetCurrentTimeMicros();
   static int64_t GetCurrentTimeMilliseconds();
+  static void Sleep(int64_t millis);
 };
 
 #endif  // BIN_UTILS_H_