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}

webrtc/tools/event_log_visualizer/plot_base.h

@@ -18,7 +18,13 @@
 namespace webrtc {
 namespace plotting {
 
-enum PlotStyle { LINE_GRAPH, LINE_DOT_GRAPH, BAR_GRAPH, LINE_STEP_GRAPH };
+enum PlotStyle {
+  LINE_GRAPH,
+  LINE_DOT_GRAPH,
+  BAR_GRAPH,
+  LINE_STEP_GRAPH,
+  DOT_GRAPH
+};
 
 struct TimeSeriesPoint {
   TimeSeriesPoint(float x, float y) : x(x), y(y) {}