Convert media constants to constexpr.

media/renderers/skcanvas_video_renderer.h

 // 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.
 
 #ifndef MEDIA_RENDERERS_SKCANVAS_VIDEO_RENDERER_H_
 #define MEDIA_RENDERERS_SKCANVAS_VIDEO_RENDERER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 70 matching lines @@
   // In general, We hold the most recently painted frame to increase the
   // performance for the case that the same frame needs to be painted
   // repeatedly. Call this function if you are sure the most recent frame will
   // never be painted again, so we can release the resource.
   void ResetCache();
 
  private:
   // Last image used to draw to the canvas.
   sk_sp<SkImage> last_image_;
   // Timestamp of the videoframe used to generate |last_image_|.
-  base::TimeDelta last_timestamp_ = media::kNoTimestamp();
+  base::TimeDelta last_timestamp_ = media::kNoTimestamp;
   // If |last_image_| is not used for a while, it's deleted to save memory.
   base::DelayTimer last_image_deleting_timer_;
 
   // Used for DCHECKs to ensure method calls executed in the correct thread.
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(SkCanvasVideoRenderer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_RENDERERS_SKCANVAS_VIDEO_RENDERER_H_