Replaced magic numbers with constants for PacketFeedback.

Bug: None
Change-Id: Ie22475227406f4e800052b52fa644ea6966db3f1
Reviewed-on: https://webrtc-review.googlesource.com/27100
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20938}
diff --git a/rtc_tools/event_log_visualizer/analyzer.cc b/rtc_tools/event_log_visualizer/analyzer.cc
index bbbde3f..21bc580 100644
--- a/rtc_tools/event_log_visualizer/analyzer.cc
+++ b/rtc_tools/event_log_visualizer/analyzer.cc
@@ -1443,7 +1443,7 @@
           float x =
               static_cast<float>(clock.TimeInMicroseconds() - begin_time_) /
               1000000;
-          if (packet.send_time_ms == -1) {
+          if (packet.send_time_ms == PacketFeedback::kNoSendTime) {
             late_feedback_series.points.emplace_back(x, prev_y);
             continue;
           }