Tracing V2 prototype [NOT FOR REVIEW]

base/trace_event/common/proto/event_args_simple.proto

+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+package tracing;
+
+message EventArgsSimple {
+  oneof arg_1_name {
+    int64 arg_1_name_idx = 1;  // This is for const char* strings.
+    string arg_1_name_string = 2;  // This is for *WithCopiedName()
+  }
+
+  oneof arg_1_value {
+    bool arg_1_bool_value = 3;
+    int64 arg_1_int_value = 4;
+    double arg_1_real_value = 5;
+  }
+
+  oneof arg_2_name {
+    int64 arg_2_name_idx = 11;  // This is for const char* strings.
+    string arg_2_name_string = 12;  // This is for *WithCopiedName()
+  }
+
+  oneof arg_2_value {
+    bool arg_2_bool_value = 13;
+    int64 arg_2_int_value = 14;
+    double arg_2_real_value = 15;
+  }
+}