Convert media constants to constexpr.

chromecast/media/cma/base/media_task_runner.h

 // Copyright 2014 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 CHROMECAST_MEDIA_CMA_BASE_MEDIA_TASK_RUNNER_H_
 #define CHROMECAST_MEDIA_CMA_BASE_MEDIA_TASK_RUNNER_H_
 
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 
 namespace chromecast {
 namespace media {
 
 class MediaTaskRunner
     : public base::RefCountedThreadSafe<MediaTaskRunner> {
  public:
   MediaTaskRunner();
 
   // Post a task with the given media |timestamp|. If |timestamp| is equal to
-  // |kNoTimestamp()|, the task is scheduled right away.
+  // |kNoTimestamp|, the task is scheduled right away.
   // How the media timestamp is used to schedule the task is an implementation
   // detail of derived classes.
   // Returns true if the task may be run at some point in the future, and false
   // if the task definitely will not be run.
   virtual bool PostMediaTask(
       const tracked_objects::Location& from_here,
       const base::Closure& task,
       base::TimeDelta timestamp) = 0;
 
  protected:
   virtual ~MediaTaskRunner();
   friend class base::RefCountedThreadSafe<MediaTaskRunner>;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MediaTaskRunner);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CMA_BASE_MEDIA_TASK_RUNNER_H_