Use persistent memory for receiving metrics from sub-processes.

chrome/browser/metrics/chrome_metrics_service_client.cc

Index: chrome/browser/metrics/chrome_metrics_service_client.cc
diff --git a/chrome/browser/metrics/chrome_metrics_service_client.cc b/chrome/browser/metrics/chrome_metrics_service_client.cc
index 968ad63d94cee348d825c5651dc01c5987ac4699..7190495094702c0340011ce2629f9e06f91f35bc 100644
--- a/chrome/browser/metrics/chrome_metrics_service_client.cc
+++ b/chrome/browser/metrics/chrome_metrics_service_client.cc
@@ -408,9 +408,11 @@ void ChromeMetricsServiceClient::Initialize() {
       metrics_state_manager_, this, g_browser_process->local_state()));
 
   // Gets access to persistent metrics shared by sub-processes.
+  std::unique_ptr<SubprocessMetricsProvider> subprocess_metrics_provider(
+      new SubprocessMetricsProvider());
+  subprocess_metrics_provider->EnableSubprocessTracking();
   metrics_service_->RegisterMetricsProvider(
-      std::unique_ptr<metrics::MetricsProvider>(
-          new SubprocessMetricsProvider()));
+      std::move(subprocess_metrics_provider));
 
   // Register metrics providers.
 #if defined(ENABLE_EXTENSIONS)