Add av_stream_get_first_dts for Chromium
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index cd7b0d9..b4a6dce 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1010,6 +1010,10 @@
  */
 int64_t    av_stream_get_end_pts(const AVStream *st);
 
+// Chromium: We use the internal field first_dts vvv
+int64_t    av_stream_get_first_dts(const AVStream *st);
+// Chromium: We use the internal field first_dts ^^^
+
 #define AV_PROGRAM_RUNNING 1
 
 /**
diff --git a/libavformat/utils.c b/libavformat/utils.c
index de7580c..0ef0fe5 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -121,6 +121,13 @@
         return AV_NOPTS_VALUE;
 }
 
+// Chromium: We use the internal field first_dts vvv
+int64_t av_stream_get_first_dts(const AVStream *st)
+{
+  return st->internal->first_dts;
+}
+// Chromium: We use the internal field first_dts ^^^
+
 struct AVCodecParserContext *av_stream_get_parser(const AVStream *st)
 {
     return st->internal->parser;