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

components/page_load_metrics/browser/metrics_web_contents_observer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_WEB_CONTENTS_OBSERVER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_WEB_CONTENTS_OBSERVER_H_
 
 #include "base/containers/scoped_ptr_map.h"
 #include "base/macros.h"
 #include "base/time/time.h"
@@ skipping 45 matching lines @@
   PAGE_LOAD_LAST_ENTRY
 };
 
 class PageLoadTracker {
  public:
   explicit PageLoadTracker(bool in_foreground);
   ~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);
 
  private:
   void RecordTimingHistograms();
 
   bool has_commit_;
 
   // We record separate metrics for events that occur after a background,
   // because metrics like layout/paint are delayed artificially
   // when they occur in the bacground.
   base::TimeTicks background_time_;
   bool started_in_foreground_;
+  bool include_in_stale_while_revalidate_experiment_;
 
   PageLoadTiming timing_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 // MetricsWebContentsObserver logs page load UMA metrics based on
 // IPC messages received from a MetricsRenderFrameObserver.
 class MetricsWebContentsObserver
     : public content::WebContentsObserver,
@@ skipping 33 matching lines @@
   base::ScopedPtrMap<content::NavigationHandle*, scoped_ptr<PageLoadTracker>>
       provisional_loads_;
   scoped_ptr<PageLoadTracker> committed_load_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserver);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_WEB_CONTENTS_OBSERVER_H_