Make new TaskRunner, SequencedTaskRunner, and SingleThreadTaskRunner interfaces

TaskRunner just has Post{,Delayed}Task(), SequencedTaskRunner
extends Executor to have ordering guarantees and PostNonNestable{,Delayed}Task(), and SingleThreadTaskRunner extends SequencedTaskRunner and guarantees execution on a single thread.

Move a bunch of methods from MessageLoopProxy into the TaskRunner classes and make it inherit from SingleThreadTaskRunner.

BUG=110973
TEST=

Review URL: https://chromiumcodereview.appspot.com/9169037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@121999 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 68 insertions, 0 deletions

diff --git a/base/task_runner.cc b/base/task_runner.cc
new file mode 100644
index 0000000..734674f
--- /dev/null
+++ b/base/task_runner.cc
@@ -0,0 +1,68 @@
+// 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.
+
+#include "base/task_runner.h"
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/threading/post_task_and_reply_impl.h"
+
+namespace base {
+
+namespace {
+
+// TODO(akalin): There's only one other implementation of
+// PostTaskAndReplyImpl in WorkerPool.  Investigate whether it'll be
+// possible to merge the two.
+class PostTaskAndReplyTaskRunner : public internal::PostTaskAndReplyImpl {
+ public:
+  PostTaskAndReplyTaskRunner(TaskRunner* destination);
+
+ private:
+  virtual bool PostTask(const tracked_objects::Location& from_here,
+                        const Closure& task) OVERRIDE;
+
+  // Non-owning.
+  TaskRunner* destination_;
+};
+
+PostTaskAndReplyTaskRunner::PostTaskAndReplyTaskRunner(
+    TaskRunner* destination) : destination_(destination) {
+  DCHECK(destination_);
+}
+
+bool PostTaskAndReplyTaskRunner::PostTask(
+    const tracked_objects::Location& from_here,
+    const Closure& task) {
+  return destination_->PostTask(from_here, task);
+}
+
+}  // namespace
+
+bool TaskRunner::PostTask(const tracked_objects::Location& from_here,
+                          const Closure& task) {
+  return PostDelayedTask(from_here, task, 0);
+}
+
+bool TaskRunner::PostTaskAndReply(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    const Closure& reply) {
+  return PostTaskAndReplyTaskRunner(this).PostTaskAndReply(
+      from_here, task, reply);
+}
+
+TaskRunner::TaskRunner() {}
+
+TaskRunner::~TaskRunner() {}
+
+void TaskRunner::OnDestruct() const {
+  delete this;
+}
+
+void TaskRunnerTraits::Destruct(const TaskRunner* task_runner) {
+  task_runner->OnDestruct();
+}
+
+}  // namespace base