Support --webrtc_test_metrics_output_path in test main().

Bug: b/260493525
Change-Id: Ic0ba5683abf467fe3671f2e673ce02867f3caf73
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/284700
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38740}
diff --git a/test/BUILD.gn b/test/BUILD.gn
index 76af19e..0908038 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -518,6 +518,7 @@
       "../api/test/metrics:chrome_perf_dashboard_metrics_exporter",
       "../api/test/metrics:global_metrics_logger_and_exporter",
       "../api/test/metrics:metrics_exporter",
+      "../api/test/metrics:metrics_set_proto_file_exporter",
       "../api/test/metrics:print_result_proxy_metrics_exporter",
       "../api/test/metrics:stdout_metrics_exporter",
       "../rtc_base",
diff --git a/test/test_main_lib.cc b/test/test_main_lib.cc
index 0ce3fb9..e0d710b 100644
--- a/test/test_main_lib.cc
+++ b/test/test_main_lib.cc
@@ -22,6 +22,7 @@
 #include "api/test/metrics/chrome_perf_dashboard_metrics_exporter.h"
 #include "api/test/metrics/global_metrics_logger_and_exporter.h"
 #include "api/test/metrics/metrics_exporter.h"
+#include "api/test/metrics/metrics_set_proto_file_exporter.h"
 #include "api/test/metrics/print_result_proxy_metrics_exporter.h"
 #include "api/test/metrics/stdout_metrics_exporter.h"
 #include "rtc_base/checks.h"
@@ -176,6 +177,12 @@
     std::vector<std::unique_ptr<test::MetricsExporter>> exporters;
     if (absl::GetFlag(FLAGS_export_perf_results_new_api)) {
       exporters.push_back(std::make_unique<test::StdoutMetricsExporter>());
+      if (!absl::GetFlag(FLAGS_webrtc_test_metrics_output_path).empty()) {
+        exporters.push_back(
+            std::make_unique<webrtc::test::MetricsSetProtoFileExporter>(
+                webrtc::test::MetricsSetProtoFileExporter::Options(
+                    absl::GetFlag(FLAGS_webrtc_test_metrics_output_path))));
+      }
       if (!absl::GetFlag(FLAGS_isolated_script_test_perf_output).empty()) {
         exporters.push_back(
             std::make_unique<test::ChromePerfDashboardMetricsExporter>(