[DO NOT COMMIT] Re-use the dafsa code for s-w-r 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 88858936ac74eabe9335ef50e51db0c72597a8ba..18cd2849a3711e83591f0cbcf10948ad8e11d964 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/page_load_metrics/page_load_metrics_initialize.h"
 
 #include "chrome/browser/page_load_metrics/observers/from_gws_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/stale_while_revalidate_metrics_observer.h"
 #include "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 #include "components/rappor/rappor_service.h"
 #include "content/public/browser/web_contents.h"
@@ -18,6 +19,11 @@ void RegisterPageLoadMetricsObservers(
   // This is a self-destruct class, and will delete itself when triggered by
   // OnPageLoadMetricsGoingAway.
   metrics->AddObserver(new FromGWSPageLoadMetricsObserver(metrics));
+  // StaleWhileRevalidateMetricsObserver also deletes itself from
+  // OnPageLoadMetricsGoingAway.
+  // TODO(ricea): Remove this in January 2016 or before.
+  metrics->AddObserver(
+      new chrome::StaleWhileRevalidateMetricsObserver(metrics));
 }
 
 }  // namespace