base: Refactor PendingTask out of MessageLoop.

base/pending_task.h

+// Copyright (c) 2011 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 PENDING_TASK_H_
+#define PENDING_TASK_H_
+#pragma once
+
+#include <queue>
+
+#include "base/callback.h"
+#include "base/location.h"
+#include "base/time.h"
+#include "base/tracking_info.h"
+
+namespace base {
+
+// Contains data about a pending task. Stored in TaskQueue and DelayedTaskQueue
+// for use by classes that queue and execute tasks.
+struct PendingTask : public TrackingInfo {
+  PendingTask(const tracked_objects::Location& posted_from,
+              const Closure& task);
+  PendingTask(const tracked_objects::Location& posted_from,
+              const Closure& task,
+              TimeTicks delayed_run_time,
+              bool nestable);
+  ~PendingTask();
+
+  // Used to support sorting.
+  bool operator<(const PendingTask& other) const;
+
+  // The task to run.
+  Closure task;
+
+  // The site this PendingTask was posted from.
+  tracked_objects::Location posted_from;
+
+  // Secondary sort key for run time.
+  int sequence_num;
+
+  // OK to dispatch from a nested loop.
+  bool nestable;
+};
+
+// Wrapper around std::queue specialized for PendingTask which adds a Swap
+// helper method.
+class TaskQueue : public std::queue<PendingTask> {
+ public:
+  void Swap(TaskQueue* queue);
+};
+
+}  // namespace base
+
+#endif  // PENDING_TASK_H_