Adding previews information to PLM UKM

chrome/browser/page_load_metrics/metrics_web_contents_observer.h

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer.h
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer.h b/chrome/browser/page_load_metrics/metrics_web_contents_observer.h
index 5d35bf3ebc7fc1ced60bdc9e4e6f185acbbdeae6..595b70c9cf7d7fe22eb3e0c0a68908ff94a63b9d 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.h
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.h
@@ -138,6 +138,12 @@ class MetricsWebContentsObserver
                        const mojom::PageLoadTiming& timing,
                        const mojom::PageLoadMetadata& metadata);
 
+  // Informs the observers of the currently committed load that the event
+  // corresponding to |event_key| has occurred. This should not be called within
+  // WebContentsObserver::DidFinishNavigation methods.
+  // This method is subject to change and may be removed in the future.
+  void BroadcastEventToObservers(const void* const event_key);
+
  private:
   friend class content::WebContentsUserData<MetricsWebContentsObserver>;