Define a protobuf format for representing plots

webrtc/tools/event_log_visualizer/graph.proto

+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+package webrtc.protobuf_plot;
+
+enum PlotStyle {
+  UNDEFINED = 0;
+  LINE_GRAPH = 1;
+  LINE_DOT_GRAPH = 2;
+  BAR_GRAPH = 3;
+};
+
+message DataSet {
+  repeated float xvalues = 1;
+  repeated float yvalues = 2;
+  optional string label = 3;
+  optional PlotStyle style = 4;
+}
+
+message Plot {
+  repeated DataSet data_sets = 1;
+  optional float xaxis_min = 2;
+  optional float xaxis_max = 3;
+  optional string xaxis_label = 4;
+  optional float yaxis_min = 5;
+  optional float yaxis_max = 6;
+  optional string yaxis_label = 7;
+  optional string title = 8;
+}
+
+message PlotCollection {
+  repeated Plot plots = 1;
+}