Visualize events related to probing in the total bitrate graph.

BUG=webrtc:6984
R=terelius@webrtc.org

Review-Url: https://codereview.webrtc.org/2782553005 .
Cr-Commit-Position: refs/heads/master@{#17449}
diff --git a/webrtc/tools/event_log_visualizer/plot_protobuf.cc b/webrtc/tools/event_log_visualizer/plot_protobuf.cc
index 6e45585..d5e9192 100644
--- a/webrtc/tools/event_log_visualizer/plot_protobuf.cc
+++ b/webrtc/tools/event_log_visualizer/plot_protobuf.cc
@@ -40,6 +40,9 @@
       data_set->set_highlight_points(true);
     } else if (series_list_[i].style == LINE_STEP_GRAPH) {
       data_set->set_style(webrtc::analytics::ChartStyle::LINE_STEP_CHART);
+    } else if (series_list_[i].style == DOT_GRAPH) {
+      data_set->set_style(webrtc::analytics::ChartStyle::SCATTER_CHART);
+      data_set->set_highlight_points(true);
     } else {
       data_set->set_style(webrtc::analytics::ChartStyle::UNDEFINED);
     }