[NoStatePrefetch] Add performance histograms.

chrome/browser/page_load_metrics/page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
index 04fb549e19dd3ffb5c19cd5e12e90c34c9703e86..6ac706be85a0eefabdb90c4347c877fcb0ed8030 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
@@ -12,6 +12,7 @@ PageLoadExtraInfo::PageLoadExtraInfo(
     bool started_in_foreground,
     bool user_gesture,
     const GURL& committed_url,
+    const GURL& start_url,
     const base::Optional<base::TimeDelta>& time_to_commit,
     UserAbortType abort_type,
     bool abort_user_initiated,
@@ -24,6 +25,7 @@ PageLoadExtraInfo::PageLoadExtraInfo(
       started_in_foreground(started_in_foreground),
       user_gesture(user_gesture),
       committed_url(committed_url),
+      start_url(start_url),
       time_to_commit(time_to_commit),
       abort_type(abort_type),
       abort_user_initiated(abort_user_initiated),