Add ChildMessageFilter, a base class for renderer/worker cross-thread MessageFilter

content/child/worker_thread_task_runner.h

+// Copyright 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 CONTENT_CHILD_WORKER_THREAD_TASK_RUNNER_H_
+#define CONTENT_CHILD_WORKER_THREAD_TASK_RUNNER_H_
+
+#include "base/task_runner.h"
+
+namespace content {
+
+// A task runner that runs tasks on a single webkit worker thread which
+// is managed by webkit_glue::WorkerTaskRunner.
+// Note that this implementation ignores the delay duration for PostDelayedTask
+// and have it behave the same as PostTask.
+class WorkerThreadTaskRunner : public base::TaskRunner {
+ public:
+  explicit WorkerThreadTaskRunner(int worker_thread_id);
+
+  // Gets the WorkerThreadTaskRunner for the current worker thread.
+  // This returns non-null value only when it is called on a worker thread.
+  static scoped_refptr<WorkerThreadTaskRunner> current();
+
+  // TaskRunner overrides.
+  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
+                               const base::Closure& task,
+                               base::TimeDelta delay) OVERRIDE;
+  virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
+
+ protected:
+  virtual ~WorkerThreadTaskRunner();
+
+ private:
+  const int worker_thread_id_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_WORKER_THREAD_TASK_RUNNER_H_