[NoStatePrefetch] Add performance histograms.

chrome/browser/page_load_metrics/page_load_metrics_initialize.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
index cc17f4cdae4259661366f0f9ab07da09d45da979..fed5a74623c79eb19208dcb05cf9406f32c9ca50 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/page_load_metrics/observers/from_gws_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/google_captcha_observer.h"
 #include "chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/stale_while_revalidate_metrics_observer.h"
@@ -78,6 +79,8 @@ void PageLoadMetricsEmbedder::RegisterObservers(
       base::WrapUnique(new HttpsEngagementPageLoadMetricsObserver(
           web_contents_->GetBrowserContext())));
   tracker->AddObserver(base::WrapUnique(new CssScanningMetricsObserver()));
+  tracker->AddObserver(
+      base::MakeUnique<NoStatePrefetchPageLoadMetricsObserver>());
 #if defined(OS_ANDROID)
   tracker->AddObserver(
       base::WrapUnique(new AndroidPageLoadMetricsObserver(web_contents_)));