[page_load_metrics] use data from WebContents::GetOpener

components/page_load_metrics/browser/metrics_web_contents_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_METRICS_WEB_CONTENTS_OBSERVER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_METRICS_WEB_CONTENTS_OBSERVER_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 95 matching lines @@
 // MetricsWebContentsObserver manages a set of provisional PageLoadTrackers, as
 // well as a committed PageLoadTracker.
 class PageLoadTracker {
  public:
   // Caller must guarantee that the embedder_interface pointer outlives this
   // class. The PageLoadTracker must not hold on to
   // currently_committed_load_or_null or navigation_handle beyond the scope of
   // 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);
   ~PageLoadTracker();
   void Redirect(content::NavigationHandle* navigation_handle);
   void Commit(content::NavigationHandle* navigation_handle);
   void FailedProvisionalLoad(content::NavigationHandle* navigation_handle);
   void WebContentsHidden();
   void WebContentsShown();
 
@@ skipping 160 matching lines @@
 
   // Tracks aborted provisional loads for a little bit longer than usual (one
   // more navigation commit at the max), in order to better understand how the
   // navigation failed. This is because most provisional loads are destroyed and
   // vanish before we get signal about what caused the abort (new navigation,
   // stop button, etc.).
   std::vector<std::unique_ptr<PageLoadTracker>> aborted_provisional_loads_;
 
   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);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_METRICS_WEB_CONTENTS_OBSERVER_H_