Buffer timing callbacks until timing state converges.

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 325 matching lines @@
   void LogAbortChainHistograms(content::NavigationHandle* final_navigation);
 
   void MaybeUpdateURL(content::NavigationHandle* navigation_handle);
 
   // Merge values from |new_paint_timing| into |merged_page_timing_|, offsetting
   // any new timings by the |navigation_start_offset|.
   void MergePaintTiming(base::TimeDelta navigation_start_offset,
                         const page_load_metrics::PaintTiming& new_paint_timing,
                         bool is_main_frame);
 
+  void DispatchTimingUpdates();
+
   UserInputTracker input_tracker_;
 
   // Whether we stopped tracking this navigation after it was initiated. We may
   // stop tracking a navigation if it doesn't meet the criteria for tracking
   // metrics in DidFinishNavigation.
   bool did_stop_tracking_;
 
   // Whether the application went into the background when this PageLoadTracker
   // was active. This is a temporary boolean for UMA tracking.
   bool app_entered_background_;
@@ skipping 33 matching lines @@
   // because metrics like layout/paint are delayed artificially
   // when they occur in the background.
   base::TimeTicks background_time_;
   base::TimeTicks foreground_time_;
   bool started_in_foreground_;
 
   // PageLoadTiming for the currently tracked page. The fields in |paint_timing|
   // are merged across all frames in the document. All other fields are for the
   // main frame document.
   PageLoadTiming merged_page_timing_;
+  PageLoadTiming last_dispatched_merged_page_timing_;
 
   PageLoadMetadata main_frame_metadata_;
+  PageLoadMetadata last_dispatched_main_frame_metadata_;
+
   PageLoadMetadata subframe_metadata_;
 
   ui::PageTransition page_transition_;
 
   base::Optional<content::GlobalRequestID> navigation_request_id_;
 
   // Whether this page load was user initiated.
   UserInitiatedInfo user_initiated_info_;
 
   // This is a subtle member. If a provisional load A gets aborted by
@@ skipping 16 matching lines @@
   // Navigation start offsets for the most recently committed document in each
   // frame.
   std::map<FrameTreeNodeId, base::TimeDelta> subframe_navigation_start_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_