Move some misc thread-related stuff from base to base/thread and into the bas...

base/threading/worker_pool.h

+// Copyright (c) 2010 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 BASE_THREADING_WORKER_POOL_H_
+#define BASE_THREADING_WORKER_POOL_H_
+#pragma once
+
+#include "base/tracked.h"
+
+class Task;
+
+namespace base {
+
+// This is a facility that runs tasks that don't require a specific thread or
+// a message loop.
+//
+// WARNING: This shouldn't be used unless absolutely necessary. We don't wait
+// for the worker pool threads to finish on shutdown, so the tasks running
+// inside the pool must be extremely careful about other objects they access
+// (MessageLoops, Singletons, etc). During shutdown these object may no longer
+// exist.
+class WorkerPool {
+ public:
+  // This function posts |task| to run on a worker thread.  |task_is_slow|
+  // should be used for tasks that will take a long time to execute.  Returns
+  // false if |task| could not be posted to a worker thread.  Regardless of
+  // return value, ownership of |task| is transferred to the worker pool.
+  static bool PostTask(const tracked_objects::Location& from_here,
+                       Task* task, bool task_is_slow);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_WORKER_POOL_H_