PageLoadMetricsObservers observe individual page loads

chrome/browser/page_load_metrics/page_load_metrics_initialize.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_PAGE_LOAD_METRICS_INITIALIZE_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_INITIALIZE_H_
 
 #include "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace rappor {
 class RapporService;
 }
 
 namespace chrome {
 
 void InitializePageLoadMetricsForWebContents(
     content::WebContents* web_contents);
 
 class PageLoadMetricsEmbedderInterfaceImpl
     : public page_load_metrics::PageLoadMetricsEmbedderInterface {
  public:
   // PageLoadMetricsEmbedderInterface:
   ~PageLoadMetricsEmbedderInterfaceImpl() override;
   rappor::RapporService* GetRapporService() override;
   bool IsPrerendering(content::WebContents* web_contents) override;
+  void RegisterObservers(
+      page_load_metrics::PageLoadMetricsObservable* metrics) override;
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_INITIALIZE_H_