[page_load_metrics] use data from WebContents::GetOpener

components/page_load_metrics/browser/metrics_web_contents_observer.h

Index: components/page_load_metrics/browser/metrics_web_contents_observer.h
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.h b/components/page_load_metrics/browser/metrics_web_contents_observer.h
index f6f9e28f2098054082b3723ad1136238b1369b0e..688b434a9dec07ba4d2d0c1c03479076fcebc11b 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.h
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.h
@@ -113,7 +113,7 @@ class PageLoadTracker {
   // the constructor.
   PageLoadTracker(bool in_foreground,
                   PageLoadMetricsEmbedderInterface* embedder_interface,
-                  PageLoadTracker* const currently_committed_load_or_null,
+                  const GURL& currently_committed_url,
                   content::NavigationHandle* navigation_handle,
                   int aborted_chain_size,
                   int aborted_chain_size_same_url);
@@ -294,6 +294,9 @@ class MetricsWebContentsObserver
 
   std::unique_ptr<PageLoadTracker> committed_load_;
 
+  // Has the MWCO observed at least one navigation?
+  bool has_navigated_;
+
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserver);
 };