Add immediate variants of doc.write page load metrics

components/page_load_metrics/browser/page_load_metrics_observer.h

 // Copyright 2015 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 COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
@@ skipping 161 matching lines @@
   virtual void OnFirstTextPaint(const PageLoadTiming& timing,
                                 const PageLoadExtraInfo& extra_info) {}
   virtual void OnFirstImagePaint(const PageLoadTiming& timing,
                                  const PageLoadExtraInfo& extra_info) {}
   virtual void OnFirstContentfulPaint(const PageLoadTiming& timing,
                                       const PageLoadExtraInfo& extra_info) {}
   virtual void OnParseStart(const PageLoadTiming& timing,
                             const PageLoadExtraInfo& extra_info) {}
   virtual void OnParseStop(const PageLoadTiming& timing,
                            const PageLoadExtraInfo& extra_info) {}
+
+  // Observer method to be invoked when there is a change in PageLoadMetadata's
+  // behavior_flags.
+  virtual void OnLoadingBehaviorObserved(
+      const page_load_metrics::PageLoadExtraInfo& extra_info) {}
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_