Buffer timing callbacks until timing state converges.

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 c696acb68da85aa746bb1d825ce0262b85e20183..80a13850377c40dd8d4db75054ca52f3a0364b72 100644
--- a/chrome/browser/page_load_metrics/page_load_tracker.h
+++ b/chrome/browser/page_load_metrics/page_load_tracker.h
@@ -343,6 +343,8 @@ class PageLoadTracker {
                         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
@@ -396,8 +398,11 @@ class PageLoadTracker {
   // 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_;