Adding previews information to PLM UKM

chrome/browser/page_load_metrics/page_load_tracker.h

Index: chrome/browser/page_load_metrics/page_load_tracker.h
diff --git a/chrome/browser/page_load_metrics/page_load_tracker.h b/chrome/browser/page_load_metrics/page_load_tracker.h
index 6146a093f37c2aa8184fead25aeed1db73836a81..187c17edd4a492db5c524c15ca1bff4e33596fb1 100644
--- a/chrome/browser/page_load_metrics/page_load_tracker.h
+++ b/chrome/browser/page_load_metrics/page_load_tracker.h
@@ -33,7 +33,6 @@ class NavigationHandle;
 namespace page_load_metrics {
 
 class PageLoadMetricsEmbedderInterface;
-class PageLoadMetricsObserver;
 
 namespace internal {
 
@@ -271,6 +270,10 @@ class PageLoadTracker : public PageLoadMetricsUpdateDispatcher::Client {
   void OnNavigationDelayComplete(base::TimeDelta scheduled_delay,
                                  base::TimeDelta actual_delay);
 
+  // Informs the observers that the event corresponding to |event_key| has
+  // occurred.
+  void BroadcastEventToObservers(const void* const event_key);
+
  private:
   // This function converts a TimeTicks value taken in the browser process
   // to navigation_start_ if: