Add a chart for packet loss on incoming streams.

Also add stream names to labels.

R=philipel@webrtc.org

Review URL: https://codereview.webrtc.org/2317113003 .

Cr-Commit-Position: refs/heads/master@{#14159}

webrtc/tools/event_log_visualizer/main.cc

@@ -128,6 +128,7 @@ int main(int argc, char* argv[]) {
 
   if (FLAGS_plot_all || FLAGS_plot_fraction_loss) {
     analyzer.CreateFractionLossGraph(collection->AppendNewPlot());
+    analyzer.CreateIncomingPacketLossGraph(collection->AppendNewPlot());
   }
 
   if (FLAGS_plot_all || FLAGS_plot_total_bitrate) {