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

native_client_sdk/src/libraries/utils/thread_safe_queue.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.
-
-#ifndef LIBRARIES_UTILS_THREAD_SAFE_QUEUE_H_
-#define LIBRARIES_UTILS_THREAD_SAFE_QUEUE_H_
-
-#include <pthread.h>
-
-#include <list>
-
-#include "utils/auto_lock.h"
-#include "utils/macros.h"
-
-
-// ThreadSafeQueue
-//
-// A simple template to support multithreaded and optionally blocking access
-// to a Queue of object pointers.
-//
-template<class T> class ThreadSafeQueue {
- public:
-  ThreadSafeQueue() {
-    pthread_mutex_init(&mutex_, NULL);
-    pthread_cond_init(&cond_, NULL);
-  }
-
-  ~ThreadSafeQueue() {
-    pthread_mutex_destroy(&mutex_);
-    pthread_cond_destroy(&cond_);
-  }
-
-  void Enqueue(T* item) {
-    AutoLock lock(&mutex_);
-    list_.push_back(item);
-
-    pthread_cond_signal(&cond_);
-  }
-
-  T* Dequeue(bool block) {
-    AutoLock lock(&mutex_);
-
-    // If blocking enabled, wait until we queue is non-empty
-    if (block) {
-      while (list_.empty()) pthread_cond_wait(&cond_, &mutex_);
-    }
-
-    if (list_.empty()) return NULL;
-
-    T* item = list_.front();
-    list_.pop_front();
-    return item;
-  }
-
- private:
-  std::list<T*> list_;
-  pthread_cond_t  cond_;
-  pthread_mutex_t mutex_;
-  DISALLOW_COPY_AND_ASSIGN(ThreadSafeQueue);
-};
-
-#endif  // LIBRARIES_UTILS_THREAD_SAFE_QUEUE_H_