Renamed and restructured the protobuf definitions for the rtc_event_log graphs.

BUG=

Review-Url: https://codereview.webrtc.org/2310403002
Cr-Commit-Position: refs/heads/master@{#14112}
diff --git a/webrtc/tools/event_log_visualizer/plot_protobuf.h b/webrtc/tools/event_log_visualizer/plot_protobuf.h
index 1ea525b..2008a22 100644
--- a/webrtc/tools/event_log_visualizer/plot_protobuf.h
+++ b/webrtc/tools/event_log_visualizer/plot_protobuf.h
@@ -10,7 +10,7 @@
 #ifndef WEBRTC_TOOLS_EVENT_LOG_VISUALIZER_PLOT_PROTOBUF_H_
 #define WEBRTC_TOOLS_EVENT_LOG_VISUALIZER_PLOT_PROTOBUF_H_
 
-#include "webrtc/tools/event_log_visualizer/graph.pb.h"
+#include "webrtc/tools/event_log_visualizer/chart.pb.h"
 #include "webrtc/tools/event_log_visualizer/plot_base.h"
 
 namespace webrtc {
@@ -21,7 +21,7 @@
   ProtobufPlot();
   ~ProtobufPlot() override;
   void Draw() override;
-  void ExportProtobuf(protobuf_plot::Plot* plot);
+  void ExportProtobuf(webrtc::analytics::Chart* chart);
 };
 
 class ProtobufPlotCollection final : public PlotCollection {
@@ -30,7 +30,7 @@
   ~ProtobufPlotCollection() override;
   void Draw() override;
   Plot* AppendNewPlot() override;
-  void ExportProtobuf(protobuf_plot::PlotCollection* collection);
+  void ExportProtobuf(webrtc::analytics::ChartCollection* collection);
 };
 
 }  // namespace plotting