Wire up packet_id / send time callbacks to webrtc via libjingle.

BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1363573002

Cr-Commit-Position: refs/heads/master@{#10289}
diff --git a/webrtc/video_engine/vie_channel_group.cc b/webrtc/video_engine/vie_channel_group.cc
index 7ed0341..a76c50a 100644
--- a/webrtc/video_engine/vie_channel_group.cc
+++ b/webrtc/video_engine/vie_channel_group.cc
@@ -445,4 +445,11 @@
       PacedSender::kDefaultPaceMultiplier * target_bitrate_bps / 1000,
       pad_up_to_bitrate_bps / 1000);
 }
+
+void ChannelGroup::OnSentPacket(const rtc::SentPacket& sent_packet) {
+  if (transport_feedback_adapter_) {
+    transport_feedback_adapter_->UpdateSendTime(sent_packet.packet_id,
+                                                sent_packet.send_time_ms);
+  }
+}
 }  // namespace webrtc