[DO NOT COMMIT] Re-use the dafsa code for s-w-r histograms

components/page_load_metrics/browser/metrics_web_contents_observer.h

Index: components/page_load_metrics/browser/metrics_web_contents_observer.h
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.h b/components/page_load_metrics/browser/metrics_web_contents_observer.h
index cf39dc9bff6e66878fc7c4cdd5f3e4a02d02ff09..066485bc26057484652b9a77ee784d4e6cea8d72 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.h
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.h
@@ -63,6 +63,12 @@ class PageLoadTracker {
   void Commit();
   void WebContentsHidden();
 
+  // If the final destination of the navigation is one of the origins included
+  // in the stale-while-revalidate experiment, call this method. See
+  // https://docs.google.com/document/d/1nBhr25nSJgoyAh4S1-U5h2sH70Iz4RR0NAfXNL79G5Y/edit
+  // for the design doc.
+  void IncludeInStaleWhileRevalidateExperiment();
+
   // Returns true if the timing was successfully updated.
   bool UpdateTiming(const PageLoadTiming& timing);
   void RecordEvent(PageLoadEvent event);
@@ -77,6 +83,7 @@ class PageLoadTracker {
   // when they occur in the bacground.
   base::TimeTicks background_time_;
   bool started_in_foreground_;
+  bool include_in_stale_while_revalidate_experiment_;
 
   PageLoadTiming timing_;