Add immediate variants of doc.write page load metrics

components/page_load_metrics/browser/metrics_web_contents_observer.cc

Index: components/page_load_metrics/browser/metrics_web_contents_observer.cc
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.cc b/components/page_load_metrics/browser/metrics_web_contents_observer.cc
index a289253e1430e014d8050cfc04194255e8c40489..736d86e9d65f1cefba0d9afd7604887135781dc1 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.cc
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.cc
@@ -207,6 +207,7 @@ void LogAbortChainSameURLHistogram(int aborted_chain_size_same_url) {
 void DispatchObserverTimingCallbacks(PageLoadMetricsObserver* observer,
                                      const PageLoadTiming& last_timing,
                                      const PageLoadTiming& new_timing,
+                                     const PageLoadMetadata& last_metadata,
                                      const PageLoadExtraInfo& extra_info) {
   observer->OnTimingUpdate(new_timing, extra_info);
   if (!new_timing.dom_content_loaded_event_start.is_zero() &&
@@ -232,6 +233,8 @@ void DispatchObserverTimingCallbacks(PageLoadMetricsObserver* observer,
     observer->OnParseStart(new_timing, extra_info);
   if (!new_timing.parse_stop.is_zero() && last_timing.parse_stop.is_zero())
     observer->OnParseStop(new_timing, extra_info);
+  if (extra_info.metadata.behavior_flags != last_metadata.behavior_flags)
+    observer->OnLoadingBehaviorObserved(extra_info);
 }
 
 }  // namespace
@@ -402,11 +405,13 @@ bool PageLoadTracker::UpdateTiming(const PageLoadTiming& new_timing,
     // the observer timing callbacks.
     const PageLoadTiming last_timing = timing_;
     timing_ = new_timing;
+
+    const PageLoadMetadata last_metadata = metadata_;
     metadata_ = new_metadata;
     const PageLoadExtraInfo info = GetPageLoadMetricsInfo();
     for (const auto& observer : observers_) {
       DispatchObserverTimingCallbacks(observer.get(), last_timing, new_timing,
-                                      info);
+                                      last_metadata, info);
     }
     return true;
   }