Convert media constants to constexpr.

media/filters/frame_processor.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 MEDIA_FILTERS_FRAME_PROCESSOR_H_
 #define MEDIA_FILTERS_FRAME_PROCESSOR_H_
 
 #include <map>
 
 #include "base/callback_forward.h"
@@ skipping 147 matching lines @@
   // discontinuity, parser reset during 'segments' mode, or switching from
   // 'sequence' to 'segments' mode.
   // Once a processed coded frame is emitted for the current coded frame group,
   // tracks the decode timestamp of the last frame emitted.
   // Explicit setting of timestampOffset will trigger subsequent notification of
   // a new coded frame start to the tracks' streams, even in 'sequence' mode, if
   // the resulting frame has a DTS less than this.
   DecodeTimestamp coded_frame_group_last_dts_ = kNoDecodeTimestamp();
 
   // Tracks the MSE coded frame processing variable of same name.
-  // Initially kNoTimestamp(), meaning "unset".
+  // Initially kNoTimestamp, meaning "unset".
   base::TimeDelta group_start_timestamp_;
 
   // Tracks the MSE coded frame processing variable of same name. It stores the
   // highest coded frame end timestamp across all coded frames in the current
   // coded frame group. It is set to 0 when the SourceBuffer object is created
   // and gets updated by ProcessFrames().
   base::TimeDelta group_end_timestamp_;
 
   UpdateDurationCB update_duration_cb_;
 
   // MediaLog for reporting messages and properties to debug content and engine.
   scoped_refptr<MediaLog> media_log_;
 
   // Counters that limit spam to |media_log_| for frame processor warnings.
   int num_dropped_preroll_warnings_ = 0;
   int num_dts_beyond_pts_warnings_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(FrameProcessor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FRAME_PROCESSOR_H_