Convert media constants to constexpr.

media/base/audio_buffer.h

 // Copyright 2013 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_BASE_AUDIO_BUFFER_H_
 #define MEDIA_BASE_AUDIO_BUFFER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 40 matching lines @@
   // must be >= 0.
   static scoped_refptr<AudioBuffer> CopyFrom(SampleFormat sample_format,
                                              ChannelLayout channel_layout,
                                              int channel_count,
                                              int sample_rate,
                                              int frame_count,
                                              const uint8_t* const* data,
                                              const base::TimeDelta timestamp);
 
   // Create an AudioBuffer with |frame_count| frames. Buffer is allocated, but
-  // not initialized. Timestamp and duration are set to kNoTimestamp().
+  // not initialized. Timestamp and duration are set to kNoTimestamp.
   static scoped_refptr<AudioBuffer> CreateBuffer(SampleFormat sample_format,
                                                  ChannelLayout channel_layout,
                                                  int channel_count,
                                                  int sample_rate,
                                                  int frame_count);
 
   // Create an empty AudioBuffer with |frame_count| frames.
   static scoped_refptr<AudioBuffer> CreateEmptyBuffer(
       ChannelLayout channel_layout,
       int channel_count,
@@ skipping 115 matching lines @@
 
   // For planar data, points to each channels data.
   std::vector<uint8_t*> channel_data_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioBuffer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_BUFFER_H_