Added is_last_packet_in_frame to match is_first_packet_in_frame.

Today we use |is_first_packet_in_frame| to know when a frame begins and the
|markerBit| to know when it ends, but the markerbit does not actually mark the
end of a frame, it marks the end of a picture.

Bug: webrtc:9361
Change-Id: Icc70e6075590cdc31e875a4eb9d489868adbb67c
Reviewed-on: https://webrtc-review.googlesource.com/100160
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24722}
diff --git a/modules/video_coding/packet.cc b/modules/video_coding/packet.cc
index 691ec62..dea72cb 100644
--- a/modules/video_coding/packet.cc
+++ b/modules/video_coding/packet.cc
@@ -28,6 +28,7 @@
       frameType(kEmptyFrame),
       codec(kVideoCodecGeneric),
       is_first_packet_in_frame(false),
+      is_last_packet_in_frame(false),
       completeNALU(kNaluUnset),
       insertStartCode(false),
       width(0),
@@ -52,6 +53,7 @@
       codec(rtpHeader.video_header().codec),
       is_first_packet_in_frame(
           rtpHeader.video_header().is_first_packet_in_frame),
+      is_last_packet_in_frame(rtpHeader.video_header().is_last_packet_in_frame),
       completeNALU(kNaluIncomplete),
       insertStartCode(rtpHeader.video_header().codec == kVideoCodecH264 &&
                       rtpHeader.video_header().is_first_packet_in_frame),