Count successes of link rel=prefetch

content/browser/loader/resource_loader.cc

Index: content/browser/loader/resource_loader.cc
diff --git a/content/browser/loader/resource_loader.cc b/content/browser/loader/resource_loader.cc
index ddb25cc1af61fb752ebeb01ce3da333058859ebd..3be9bf4fc8b42861d0d0d12671b35133c698ec0a 100644
--- a/content/browser/loader/resource_loader.cc
+++ b/content/browser/loader/resource_loader.cc
@@ -744,6 +744,9 @@ void ResourceLoader::RecordHistograms() {
     }
 
     UMA_HISTOGRAM_ENUMERATION("Net.Prefetch.Pattern", status, STATUS_MAX);
+  } else if (request_->response_info().unused_since_prefetch) {
+    TimeDelta total_time = base::TimeTicks::Now() - request_->creation_time();
+    UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeSpentOnPrefetchHit", total_time);
   }
 }