Add StaleWhileRevalidateExperiment histograms.

chrome/browser/page_load_metrics/observers/stale_while_revalidate_metrics_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 CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_FROM_GWS_PAGE_LOAD_METRICS_OBSERVER_H_
-#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_FROM_GWS_PAGE_LOAD_METRICS_OBSERVER_H_
+#ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_STALE_WHILE_REVALIDATE_METRICS_OBSERVER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_STALE_WHILE_REVALIDATE_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
 #include "components/page_load_metrics/browser/page_load_metrics_observer.h"
 
-class FromGWSPageLoadMetricsObserver
+namespace chrome {
+
+class StaleWhileRevalidateMetricsObserver
     : public page_load_metrics::PageLoadMetricsObserver {
  public:
-  explicit FromGWSPageLoadMetricsObserver(
+  explicit StaleWhileRevalidateMetricsObserver(
       page_load_metrics::PageLoadMetricsObservable* metrics);
   // page_load_metrics::PageLoadMetricsObserver implementation:
   void OnCommit(content::NavigationHandle* navigation_handle) override;
   void OnComplete(
       const page_load_metrics::PageLoadTiming& timing,
       const page_load_metrics::PageLoadExtraInfo& extra_info) override;
   void OnPageLoadMetricsGoingAway() override;
 
- protected:
-  // Called in tests.
-  void SetCommittedURLAndReferrer(const GURL& url,
-                                  const content::Referrer& referrer);
-
  private:
-  bool navigation_from_gws_;
+  // True if the committed URL is one of the domains of interest to the
+  // stale-while-revalidate experiment.
+  bool is_interesting_domain_;
   page_load_metrics::PageLoadMetricsObservable* const metrics_;
 
-  DISALLOW_COPY_AND_ASSIGN(FromGWSPageLoadMetricsObserver);
+  DISALLOW_COPY_AND_ASSIGN(StaleWhileRevalidateMetricsObserver);
 };
 
-#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_FROM_GWS_PAGE_LOAD_METRICS_OBSERVER_H_
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_STALE_WHILE_REVALIDATE_METRICS_OBSERVER_H_