[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..e9999ddd72d316630868ebd7cb106fd8094ce3ad 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 commit?
+  bool has_commit_;

[Bryan McQuade, 2016/04/26 18:36:39]

any reason not to instead track whether at least one navigation has been
initiated instead (in DidStartNavigation rather than DidFinishNavigation)? if
the first nav fails to commit and then the user issues a second nav (e.g. types
a URL in the URL bar) we would not want to track that second nav as being
associated with the opener iiuc.

[Charlie Harrison, 2016/04/26 19:02:41]

Hm yeah I think you're right. We only want to use the opener for the last
committed load once (in OnStart).

+
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserver);
 };