Plot accumelated packets over time.

BUG=

Review-Url: https://codereview.webrtc.org/2295063006
Cr-Commit-Position: refs/heads/master@{#14066}
diff --git a/webrtc/tools/event_log_visualizer/main.cc b/webrtc/tools/event_log_visualizer/main.cc
index d8d9e25..a56947c 100644
--- a/webrtc/tools/event_log_visualizer/main.cc
+++ b/webrtc/tools/event_log_visualizer/main.cc
@@ -91,10 +91,16 @@
     if (FLAGS_incoming) {
       analyzer.CreatePacketGraph(webrtc::PacketDirection::kIncomingPacket,
                                  collection->AppendNewPlot());
+      analyzer.CreateAccumulatedPacketsGraph(
+          webrtc::PacketDirection::kIncomingPacket,
+          collection->AppendNewPlot());
     }
     if (FLAGS_outgoing) {
       analyzer.CreatePacketGraph(webrtc::PacketDirection::kOutgoingPacket,
                                  collection->AppendNewPlot());
+      analyzer.CreateAccumulatedPacketsGraph(
+          webrtc::PacketDirection::kOutgoingPacket,
+          collection->AppendNewPlot());
     }
   }