UMA for measuring how often 2 or more tabs script the same background contents.

chrome/browser/background/background_contents.h

 // Copyright (c) 2011 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 CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_
 #define CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "extensions/browser/deferred_start_render_host.h"
 #include "ui/base/window_open_disposition.h"
 #include "url/gurl.h"
 
 class Profile;
 
 namespace content {
+class RenderFrameHost;
 class SessionStorageNamespace;
 };
 
 namespace extensions {
 class ExtensionHostDelegate;
 }
 
 // This class maintains a WebContents used in the background. It can host a
 // renderer, but does not have any visible display.
 // TODO(atwilson): Unify this with background pages; http://crbug.com/77790
@@ skipping 77 matching lines @@
 
   Profile* profile_;
   std::unique_ptr<content::WebContents> web_contents_;
   content::NotificationRegistrar registrar_;
   base::ObserverList<extensions::DeferredStartRenderHostObserver>
       deferred_start_render_host_observer_list_;
 
   // The initial URL to load.
   GURL initial_url_;
 
+  // TODO(lukasza): Remove members below after gathering sufficient UMA data for
+  // https://crbug.com/721947.
+  void DidChangeOpener() override;
+  void TrackPreviousOpener();
+  void OnPreviousOpenerDestroyed();
+  bool IsCurrentOpenerHostedApp();
+  content::RenderFrameHost* previous_opener_ = nullptr;
+  base::WeakPtrFactory<BackgroundContents> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(BackgroundContents);
 };
 
 // This is the data sent out as the details with BACKGROUND_CONTENTS_OPENED.
 struct BackgroundContentsOpenedDetails {
   // The BackgroundContents object that has just been opened.
   BackgroundContents* contents;
 
   // The name of the parent frame for these contents.
   const std::string& frame_name;
 
   // The ID of the parent application (if any).
   const base::string16& application_id;
 };
 
 #endif  // CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_