Framing for a DOMStorage backend that does not depend on in-process-webkit.

webkit/dom_storage/dom_storage_task_runner.h

+// Copyright (c) 2012 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 WEBKIT_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_
+#define WEBKIT_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_
+#pragma once
+
+#include "base/memory/ref_counted.h"
+#include "base/threading/sequenced_worker_pool.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace dom_storage {
+
+// Tasks must run serially with respect to one another, but may

[darin (slow to review), 2012/02/04 05:26:07]

there's actually work underway by akalin to create *TaskRunner classes:  one
that will replace MessageLoopProxy and one that will wrap SequencedWorkerPool!

+// execute on different OS threads. The base class is implemented
+// in terms of a MessageLoopProxy for use in testing.
+class DomStorageTaskRunner
+    : public base::RefCountedThreadSafe<DomStorageTaskRunner> {
+ public:
+  explicit DomStorageTaskRunner(base::MessageLoopProxy* message_loop);
+  virtual ~DomStorageTaskRunner();
+
+  // Schedules a task to be run immediately.
+  virtual void PostTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task);
+
+  // Schedules a task to be run after a delay.
+  virtual void PostDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task,
+      base::TimeDelta delay);
+
+ protected:
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+};
+
+// A derived class that utlizes the SequenceWorkerPool under a
+// dom_storage specific SequenceToken. The MessageLoopProxy
+// is used to delay scheduling on the worker pool.
+class DomStorageWorkerPoolTaskRunner : public DomStorageTaskRunner {
+ public:
+  DomStorageWorkerPoolTaskRunner(
+      base::SequencedWorkerPool* sequenced_worker_pool,
+      base::MessageLoopProxy* delayed_task_loop);
+  virtual ~DomStorageWorkerPoolTaskRunner();
+
+  // Schedules a sequenced worker task to be run immediately.
+  virtual void PostTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task) OVERRIDE;
+
+  // Schedules a sequenced worker task to be run after a delay.
+  virtual void PostDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task,
+      base::TimeDelta delay) OVERRIDE;
+
+ private:
+  base::SequencedWorkerPool* sequenced_worker_pool_;  // not owned
+  base::SequencedWorkerPool::SequenceToken sequence_token_;
+};
+
+}  // namespace dom_storage
+
+#endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_