In RtpVideoStreamReceiver change way to track time for the last received packet.

Instead of tracking packets accepted by PacketBuffer, track all incoming
packets, including packets discarded before getting into PacketBuffer.

Bug: b/179759126
Change-Id: I4d270c61455608fb78b0df8f27760868f4c98205
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208289
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33305}
diff --git a/video/rtp_video_stream_receiver2.cc b/video/rtp_video_stream_receiver2.cc
index 9834e06..3601d1d 100644
--- a/video/rtp_video_stream_receiver2.cc
+++ b/video/rtp_video_stream_receiver2.cc
@@ -913,7 +913,8 @@
 }
 
 absl::optional<int64_t> RtpVideoStreamReceiver2::LastReceivedPacketMs() const {
-  return packet_buffer_.LastReceivedPacketMs();
+  RTC_DCHECK_RUN_ON(&worker_task_checker_);
+  return last_received_rtp_system_time_ms_;
 }
 
 absl::optional<int64_t> RtpVideoStreamReceiver2::LastReceivedKeyframePacketMs()