Send an event to the page load metrics to track resource starting.

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 9d486db8a5122bcd4f92272273d97acc97ab4e70..e8a551f61e4b256fdad5703a972a833ea43db8d4 100644
--- a/chrome/browser/page_load_metrics/page_load_tracker.h
+++ b/chrome/browser/page_load_metrics/page_load_tracker.h
@@ -182,7 +182,9 @@ class PageLoadTracker {
   // UpdateTiming.
   void UpdateChildFrameMetadata(const PageLoadMetadata& child_metadata);
 
-  void OnLoadedResource(const ExtraRequestInfo& extra_request_info);
+  void OnStartedResource(const ExtraRequestStartInfo& extra_request_info);
+
+  void OnLoadedResource(const ExtraRequestCompleteInfo& extra_request_info);
 
   // Signals that we should stop tracking metrics for the associated page load.
   // We may stop tracking a page load if it doesn't meet the criteria for