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_buffer.cc b/modules/video_coding/packet_buffer.cc
index e1172b3..fe93fb3 100644
--- a/modules/video_coding/packet_buffer.cc
+++ b/modules/video_coding/packet_buffer.cc
@@ -107,7 +107,7 @@
     }
 
     sequence_buffer_[index].frame_begin = packet->is_first_packet_in_frame;
-    sequence_buffer_[index].frame_end = packet->markerBit;
+    sequence_buffer_[index].frame_end = packet->is_last_packet_in_frame;
     sequence_buffer_[index].seq_num = packet->seqNum;
     sequence_buffer_[index].continuous = false;
     sequence_buffer_[index].frame_created = false;