Adding previews information to PLM UKM

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 1c0c832cf8765c61f1a60cc83bc1fc34df6b6a28..9187e0b91f3b8b15a4b0e16f4aefffd967d7ea52 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
@@ -34,6 +34,7 @@
 #include "chrome/browser/page_load_metrics/observers/omnibox_suggestion_used_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/prerender_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/previews_ukm_observer.h"
 #include "chrome/browser/page_load_metrics/observers/protocol_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/subresource_filter_metrics_observer.h"
@@ -98,6 +99,7 @@ void PageLoadMetricsEmbedder::RegisterObservers(
         base::MakeUnique<MultiTabLoadingPageLoadMetricsObserver>());
     tracker->AddObserver(
         base::MakeUnique<previews::PreviewsPageLoadMetricsObserver>());
+    tracker->AddObserver(base::MakeUnique<previews::PreviewsUKMObserver>());
     tracker->AddObserver(
         base::MakeUnique<ServiceWorkerPageLoadMetricsObserver>());
     tracker->AddObserver(base::MakeUnique<SubresourceFilterMetricsObserver>());