Change the thread interface in runtime/platform and use it starting all threads

runtime/bin/thread_pool_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 BIN_THREAD_POOL_WIN_H_
-#define BIN_THREAD_POOL_WIN_H_
-
-#if !defined(BIN_THREAD_POOL_H_)
-#error Do not include thread_pool_win.h directly; use thread_pool.h instead.
-#endif
-
-#include "platform/globals.h"
-
-class ThreadPoolData {
- private:
-  static const int kMaxThreadPoolSize = 16;
-
-  ThreadPoolData() { UNIMPLEMENTED(); }
-  ~ThreadPoolData() {}
-
-  friend class ThreadPool;
-
-  DISALLOW_ALLOCATION();
-  DISALLOW_COPY_AND_ASSIGN(ThreadPoolData);
-};
-
-#endif  // BIN_THREAD_POOL_WIN_H_