Move thread_pool.h into utils so it can be shared by more than one example.

native_client_sdk/src/examples/demo/voronoi/threadpool.h

-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Simple thread pool class
-
-#ifndef EXAMPLES_DEMO_VORONOI_THREADPOOL_H_
-#define EXAMPLES_DEMO_VORONOI_THREADPOOL_H_
-
-#include <pthread.h>
-#include <semaphore.h>
-
-// typdef helper for work function
-typedef void (*WorkFunction)(int task_index, void* data);
-
-// ThreadPool is a class to manage num_threads and assign
-// them num_tasks of work at a time. Each call
-// to Dispatch(..) will block until all tasks complete.
-// If 0 is passed in for num_threads, all tasks will be
-// issued on the dispatch thread.
-
-class ThreadPool {
- public:
-  void Dispatch(int num_tasks, WorkFunction work, void* data);
-  explicit ThreadPool(int num_threads);
-  ~ThreadPool();
- private:
-  int DecCounter();
-  void Setup(int counter, WorkFunction work, void* data);
-  void DispatchMany(int num_tasks, WorkFunction work, void* data);
-  void DispatchHere(int num_tasks, WorkFunction work, void* data);
-  void WorkLoop();
-  static void* WorkerThreadEntry(void* data);
-  void PostExitAndJoinAll();
-  pthread_t* threads_;
-  int counter_;
-  const int num_threads_;
-  bool exiting_;
-  void* user_data_;
-  WorkFunction user_work_function_;
-  sem_t work_sem_;
-  sem_t done_sem_;
-};
-#endif  // EXAMPLES_DEMO_VORONOI_THREADPOOL_H_
-