Convert media constants to constexpr.

media/filters/source_buffer_stream.h

Index: media/filters/source_buffer_stream.h
diff --git a/media/filters/source_buffer_stream.h b/media/filters/source_buffer_stream.h
index 2d5017cd611a0dbb88d11576aa14d481f909af93..52d12aaf7e2ab280a306e0badf264772c983be2e 100644
--- a/media/filters/source_buffer_stream.h
+++ b/media/filters/source_buffer_stream.h
@@ -211,7 +211,7 @@ class MEDIA_EXPORT SourceBufferStream {
       DecodeTimestamp first_timestamp, DecodeTimestamp second_timestamp) const;
 
   // Helper method that returns the timestamp for the next buffer that
-  // |selected_range_| will return from GetNextBuffer() call, or kNoTimestamp()
+  // |selected_range_| will return from GetNextBuffer() call, or kNoTimestamp
   // if in between seeking (i.e. |selected_range_| is null).
   DecodeTimestamp GetNextBufferTimestamp();
 
@@ -272,14 +272,14 @@ class MEDIA_EXPORT SourceBufferStream {
 
   // Find a keyframe timestamp that is >= |start_timestamp| and can be used to
   // find a new selected range.
-  // Returns kNoTimestamp() if an appropriate keyframe timestamp could not be
+  // Returns kNoTimestamp if an appropriate keyframe timestamp could not be
   // found.
   DecodeTimestamp FindNewSelectedRangeSeekTimestamp(
       const DecodeTimestamp start_timestamp);
 
   // Searches |ranges_| for the first keyframe timestamp that is >= |timestamp|.
   // If |ranges_| doesn't contain a GOP that covers |timestamp| or doesn't
-  // have a keyframe after |timestamp| then kNoTimestamp() is returned.
+  // have a keyframe after |timestamp| then kNoTimestamp is returned.
   DecodeTimestamp FindKeyframeAfterTimestamp(const DecodeTimestamp timestamp);
 
   // Returns "VIDEO" for a video SourceBufferStream, "AUDIO" for an audio
@@ -419,7 +419,7 @@ class MEDIA_EXPORT SourceBufferStream {
   // The timestamp of the last buffer appended to the coded frame group, set to
   // kNoDecodeTimestamp() if the beginning of the group.
   DecodeTimestamp last_appended_buffer_timestamp_ = kNoDecodeTimestamp();
-  base::TimeDelta last_appended_buffer_duration_ = kNoTimestamp();
+  base::TimeDelta last_appended_buffer_duration_ = kNoTimestamp;
   bool last_appended_buffer_is_keyframe_ = false;
 
   // The decode timestamp on the last buffer returned by the most recent