Buffer cross frame paint timing updates.

chrome/browser/page_load_metrics/page_load_tracker.cc

Index: chrome/browser/page_load_metrics/page_load_tracker.cc
diff --git a/chrome/browser/page_load_metrics/page_load_tracker.cc b/chrome/browser/page_load_metrics/page_load_tracker.cc
index b3c4f643525cce773c7e57ba7ffc3cd6b75a8ec9..a781d58d01c8382845c26da3e909403d3a669fdc 100644
--- a/chrome/browser/page_load_metrics/page_load_tracker.cc
+++ b/chrome/browser/page_load_metrics/page_load_tracker.cc
@@ -198,6 +198,8 @@ PageLoadTracker::~PageLoadTracker() {
   if (did_stop_tracking_)
     return;
 
+  metrics_update_dispatcher_.ShutDown();

[Charlie Harrison, 2017/05/30 14:49:07]

optional: It seems a bit strange to have a Shutdown() method called in the
destructor. What about having the dispatcher just be a unique_ptr and call reset
here?

[Bryan McQuade, 2017/05/30 15:30:23]

It's not that unusual / strange - see
https://cs.chromium.org/search/?q=::~+Shutdown

+
   if (page_end_time_.is_null()) {
     // page_end_time_ can be unset in some cases, such as when a navigation is
     // aborted by a navigation that started before it. In these cases, set the