Update OnCommit to return ObservePolicy.

chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h

Index: chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h
diff --git a/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h b/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h
index 3ce06e41480b5a503324735b53dce882024fe550..17facaf8d63318eebc61174e831b240d169a0993 100644
--- a/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h
+++ b/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h
@@ -40,7 +40,7 @@ class PreviewsPageLoadMetricsObserver
   ~PreviewsPageLoadMetricsObserver() override;
 
   // page_load_metrics::PageLoadMetricsObserver:
-  void OnCommit(content::NavigationHandle* navigation_handle) override;
+  ObservePolicy OnCommit(content::NavigationHandle* navigation_handle) override;
   void OnDomContentLoadedEventStart(
       const page_load_metrics::PageLoadTiming& timing,
       const page_load_metrics::PageLoadExtraInfo& info) override;
@@ -60,9 +60,6 @@ class PreviewsPageLoadMetricsObserver
   // testing.
   virtual bool IsOfflinePreview(content::WebContents* web_contents) const;
 
-  // Whether this page load was an offline pages preview.
-  bool is_offline_preview_;
-
   DISALLOW_COPY_AND_ASSIGN(PreviewsPageLoadMetricsObserver);
 };