Introduce DecodeTimestamp class to make it easier to distiguish presentation and decode timestamps.

media/formats/mp2t/es_parser_h264_unittest.cc

Index: media/formats/mp2t/es_parser_h264_unittest.cc
diff --git a/media/formats/mp2t/es_parser_h264_unittest.cc b/media/formats/mp2t/es_parser_h264_unittest.cc
index 2c13df0d853fb72b12efe2640000ebd63ca95e97..2ac94c79943ec6393dad615e61c4d932e40ed6cb 100644
--- a/media/formats/mp2t/es_parser_h264_unittest.cc
+++ b/media/formats/mp2t/es_parser_h264_unittest.cc
@@ -206,7 +206,7 @@ void EsParserH264Test::ProcessPesPackets(
     size_t cur_pes_size = pes_packets[k].size;
 
     base::TimeDelta pts = kNoTimestamp();
-    base::TimeDelta dts = kNoTimestamp();
+    DecodeTimestamp dts = kNoDecodeTimestamp();
     if (pes_packets[k].pts >= base::TimeDelta() || force_timing)
       pts = pes_packets[k].pts;
 
@@ -297,4 +297,3 @@ TEST_F(EsParserH264Test, SeveralPesPerAccessUnit) {
 
 }  // namespace mp2t
 }  // namespace media
-