Create base::WorkerPoolJob. Use it for HostResolverImpl and DirectoryLister.

base/worker_pool_job.cc

+// 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.
+
+#include "base/worker_pool_job.h"
+
+#include "base/logging.h"
+#include "base/message_loop_proxy.h"
+#include "base/worker_pool.h"
+
+namespace base {
+
+WorkerPoolJob::WorkerPoolJob()
+    : origin_loop_(base::MessageLoopProxy::CreateForCurrentThread()),
+      canceled_(false),
+      state_(NONE) {}
+
+WorkerPoolJob::~WorkerPoolJob() {}
+
+void WorkerPoolJob::StartJob() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_EQ(state_, NONE);

[eroman, 2011/01/05 01:24:52]

Can the state DCHECK be more restrictive?

i.e, I don't think we want to transition from RUNNING --> RUNNING.

Also it isn't clear that it would be valid to call StartJob() more than once.

(For example if we wanted to allow calling StartJob() after cancellation, it
should reset canceled_).

+  state_ = RUNNING;
+  bool posted = WorkerPool::PostTask(
+      FROM_HERE,
+      NewRunnableMethod(this, &WorkerPoolJob::RunJobOnWorkerPool),
+      true /* is_slow */);
+  DCHECK(posted);
+}
+
+void WorkerPoolJob::CancelJob() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_NE(state_, NONE);
+  DCHECK_NE(state_, DONE);

[eroman, 2011/01/05 01:24:52]

Can these two checks be combined into:
DCHECK_EQ(RUNNING, state_)

+  DCHECK(!canceled_);
+  canceled_ = true;
+}
+
+bool WorkerPoolJob::canceled() const {
+  // No thread check since RunJob() implementations may check to see if they've
+  // been canceled so they can bail out early.

[eroman, 2011/01/05 01:24:52]

I don't think this comment is true anymore.

+  DCHECK_NE(state_, NONE);
+  return canceled_;
+}
+
+void WorkerPoolJob::RunJobOnWorkerPool() {
+  DCHECK(!thread_checker_.CalledOnValidThread());
+
+  RunJob();
+
+  origin_loop_->PostTask(
+      FROM_HERE,
+      NewRunnableMethod(this, &WorkerPoolJob::CompleteJobOnOriginLoop));
+}
+
+void WorkerPoolJob::CompleteJobOnOriginLoop() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_NE(state_, NONE);

[eroman, 2011/01/05 01:24:52]

Can these two statnments be combined into:

DCHECK_EQ(RUNNING, state_)

+  DCHECK_NE(state_, DONE);
+
+  // No need to lock, since writes only happen on origin loop.
+  if (canceled_) {
+    state_ = DONE;
+    return;
+  }
+
+  OnJobCompleted();
+
+  state_ = DONE;

[eroman, 2011/01/05 01:24:52]

nit: I wander if you want to set state_ to DONE before calling OnJobCompleted(),
to catch if we try to cancel/start the job again inside that handler.

+}
+
+}  // namespace base