Add support for counting same-document AMP loads.

chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc
index b1b2c49c5f60fb9edf8e7bbd0a28d2fd7ce9a879..cd38fd5fb545931ab0dbeff072e7502aa1c5de68 100644
--- a/chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.cc
@@ -86,8 +86,7 @@ AdsPageLoadMetricsObserver::OnCommit(
   return CONTINUE_OBSERVING;
 }
 
-page_load_metrics::PageLoadMetricsObserver::ObservePolicy
-AdsPageLoadMetricsObserver::OnDidFinishSubFrameNavigation(
+void AdsPageLoadMetricsObserver::OnDidFinishSubFrameNavigation(
     content::NavigationHandle* navigation_handle) {
   // Determine if the frame is part of an existing ad, the root of a new ad,
   // or a non-ad frame. Once a frame is labled as an ad, it is always
@@ -110,7 +109,7 @@ AdsPageLoadMetricsObserver::OnDidFinishSubFrameNavigation(
             "PageLoad.Clients.Ads.Google.Navigations.AdFrameRenavigatedToAd",
             FrameIsAd(navigation_handle));
       }
-      return CONTINUE_OBSERVING;
+      return;
     }
     // This frame was previously not an ad, process it as usual. If it had
     // any child frames that were ads, those will still be recorded.
@@ -134,7 +133,6 @@ AdsPageLoadMetricsObserver::OnDidFinishSubFrameNavigation(
   ad_frames_data_[frame_tree_node_id] = ad_data;
 
   ProcessOngoingNavigationResource(frame_tree_node_id);
-  return CONTINUE_OBSERVING;
 }
 
 page_load_metrics::PageLoadMetricsObserver::ObservePolicy