Convert media constants to constexpr.

media/base/decoder_buffer.h

Index: media/base/decoder_buffer.h
diff --git a/media/base/decoder_buffer.h b/media/base/decoder_buffer.h
index 64a881093343111d9e77dce584bc105491906c51..d100db0595409ecc1e22b406be60eb5cab7a8b3b 100644
--- a/media/base/decoder_buffer.h
+++ b/media/base/decoder_buffer.h
@@ -86,8 +86,8 @@ class MEDIA_EXPORT DecoderBuffer
 
   void set_duration(base::TimeDelta duration) {
     DCHECK(!end_of_stream());
-    DCHECK(duration == kNoTimestamp() ||
-           (duration >= base::TimeDelta() && duration != kInfiniteDuration()))
+    DCHECK(duration == kNoTimestamp ||
+           (duration >= base::TimeDelta() && duration != kInfiniteDuration))
         << duration.InSecondsF();
     duration_ = duration;
   }
@@ -119,7 +119,7 @@ class MEDIA_EXPORT DecoderBuffer
 
   // A discard window indicates the amount of data which should be discard from
   // this buffer after decoding.  The first value is the amount of the front and
-  // the second the amount off the back.  A value of kInfiniteDuration() for the
+  // the second the amount off the back.  A value of kInfiniteDuration for the
   // first value indicates the entire buffer should be discarded; the second
   // value must be base::TimeDelta() in this case.
   typedef std::pair<base::TimeDelta, base::TimeDelta> DiscardPadding;
@@ -149,13 +149,13 @@ class MEDIA_EXPORT DecoderBuffer
   }
 
   // Indicates this buffer is part of a splice around |splice_timestamp_|.
-  // Returns kNoTimestamp() if the buffer is not part of a splice.
+  // Returns kNoTimestamp if the buffer is not part of a splice.
   base::TimeDelta splice_timestamp() const {
     DCHECK(!end_of_stream());
     return splice_timestamp_;
   }
 
-  // When set to anything but kNoTimestamp() indicates this buffer is part of a
+  // When set to anything but kNoTimestamp indicates this buffer is part of a
   // splice around |splice_timestamp|.
   void set_splice_timestamp(base::TimeDelta splice_timestamp) {
     DCHECK(!end_of_stream());