[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 c6c0a26d162cc82a01270b1d1356ed550645bbde..7f98474b3b2a1d0891835082375fd62a771d158b 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 "content/public/browser/web_contents.h"
 
@@ -17,6 +18,9 @@ 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.

[tyoshino (SeeGerritForStatus), 2015/11/04 08:34:07]

merge with the comments at L18-19?

[Adam Rice, 2015/11/05 05:30:39]

The FromGWS metrics are permanent, but the StaleWhileRevalidate ones should be
removed after 1 or 2 releases. To make it easy to remove, I'd rather not change
the comment above.

[tyoshino (SeeGerritForStatus), 2015/11/05 09:00:02]

Ah, got it!

+  metrics->AddObserver(new StaleWhileRevalidateMetricsObserver(metrics));
 }
 
 }  // namespace