Chromecast: split DummyMediaTaskRunner class into its own file.

chromecast/media/cma/base/simple_media_task_runner.cc

+// Copyright 2015 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 "chromecast/media/cma/base/simple_media_task_runner.h"
+
+#include "base/single_thread_task_runner.h"
+
+namespace chromecast {
+namespace media {
+
+SimpleMediaTaskRunner::SimpleMediaTaskRunner(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
+    : task_runner_(task_runner) {
+}
+
+SimpleMediaTaskRunner::~SimpleMediaTaskRunner() {
+}
+
+bool SimpleMediaTaskRunner::PostMediaTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta timestamp) {
+  return task_runner_->PostTask(from_here, task);
+}
+
+}  // namespace media
+}  // namespace chromecast