PageLoadMetricsObservers observe individual page loads

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_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"
 
 namespace chrome {
 
 class StaleWhileRevalidateMetricsObserver
     : public page_load_metrics::PageLoadMetricsObserver {
  public:
-  explicit StaleWhileRevalidateMetricsObserver(
-      page_load_metrics::PageLoadMetricsObservable* metrics);
+  StaleWhileRevalidateMetricsObserver();
   // 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;
 
  private:
   // 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(StaleWhileRevalidateMetricsObserver);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_STALE_WHILE_REVALIDATE_METRICS_OBSERVER_H_