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

chrome/browser/page_load_metrics/page_load_tracker.cc

 // Copyright 2016 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.
 
 #include "chrome/browser/page_load_metrics/page_load_tracker.h"
 
 #include <algorithm>
 #include <ostream>
 #include <string>
 #include <utility>
@@ skipping 543 matching lines @@
     const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
     for (const auto& observer : observers_) {
       DispatchObserverTimingCallbacks(observer.get(), last_timing, new_timing,
                                       last_metadata, info);
     }
     return true;
   }
   return false;
 }
 
+void PageLoadTracker::OnStartedResource(
+    const ExtraRequestInfo& extra_request_info) {
+  for (const auto& observer : observers_) {
+    observer->OnStartedResource(extra_request_info);
+  }
+}
+
 void PageLoadTracker::OnLoadedResource(
     const ExtraRequestInfo& extra_request_info) {
   for (const auto& observer : observers_) {
     observer->OnLoadedResource(extra_request_info);
   }
 }
 
 void PageLoadTracker::StopTracking() {
   did_stop_tracking_ = true;
   observers_.clear();
@@ skipping 159 matching lines @@
 }
 
 void PageLoadTracker::MediaStartedPlaying(
     const content::WebContentsObserver::MediaPlayerInfo& video_type,
     bool is_in_main_frame) {
   for (const auto& observer : observers_)
     observer->MediaStartedPlaying(video_type, is_in_main_frame);
 }
 
 }  // namespace page_load_metrics