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

chrome/browser/page_load_metrics/page_load_tracker.h

 // 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 151 matching lines @@
 
   // Returns true if the timing was successfully updated.
   bool UpdateTiming(const PageLoadTiming& timing,
                     const PageLoadMetadata& metadata);
 
   // Update metadata for child frames. Updates for child frames arrive
   // separately from updates for the main frame, so aren't included in
   // UpdateTiming.
   void UpdateChildFrameMetadata(const PageLoadMetadata& child_metadata);
 
+  void OnStartedResource(const ExtraRequestInfo& extra_request_info);
+
   void OnLoadedResource(const ExtraRequestInfo& 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
   // tracking metrics in DidFinishNavigation.
   void StopTracking();
 
   int aborted_chain_size() const { return aborted_chain_size_; }
   int aborted_chain_size_same_url() const {
     return aborted_chain_size_same_url_;
@@ skipping 152 matching lines @@
   PageLoadMetricsEmbedderInterface* const embedder_interface_;
 
   std::vector<std::unique_ptr<PageLoadMetricsObserver>> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_