Convert media constants to constexpr.

media/base/timestamp_constants.h

Index: media/base/timestamp_constants.h
diff --git a/media/base/timestamp_constants.h b/media/base/timestamp_constants.h
index f5a1ab5d3ac65b85f0bb3ccc80fabb29a7ae0bff..a38fc44667b3ac914113338e89ac49b18e9b91db 100644
--- a/media/base/timestamp_constants.h
+++ b/media/base/timestamp_constants.h
@@ -10,19 +10,16 @@
 #include <limits>
 
 #include "base/time/time.h"
-#include "media/base/media_export.h"
 
 namespace media {
 
 // Indicates an invalid or missing timestamp.
-MEDIA_EXPORT inline base::TimeDelta kNoTimestamp() {
-  return base::TimeDelta::FromMicroseconds(std::numeric_limits<int64_t>::min());
-}
+constexpr base::TimeDelta kNoTimestamp =
+    base::TimeDelta::FromMicroseconds(std::numeric_limits<int64_t>::min());
 
 // Represents an infinite stream duration.
-MEDIA_EXPORT inline base::TimeDelta kInfiniteDuration() {
-  return base::TimeDelta::Max();
-}
+constexpr base::TimeDelta kInfiniteDuration =
+    base::TimeDelta::FromMicroseconds(std::numeric_limits<int64_t>::max());
 
 }  // namespace media