Hidden windows should not keep Chrome alive.

chrome/browser/ui/apps/chrome_app_delegate.h

 // Copyright 2014 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_UI_APPS_CHROME_APP_DELEGATE_H_
 #define CHROME_BROWSER_UI_APPS_CHROME_APP_DELEGATE_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/public/browser/notification_observer.h"
@@ skipping 44 matching lines @@
   bool CheckMediaAccessPermission(
       content::WebContents* web_contents,
       const GURL& security_origin,
       content::MediaStreamType type,
       const extensions::Extension* extension) override;
   int PreferredIconSize() override;
   void SetWebContentsBlocked(content::WebContents* web_contents,
                              bool blocked) override;
   bool IsWebContentsVisible(content::WebContents* web_contents) override;
   void SetTerminatingCallback(const base::Closure& callback) override;
+  void OnHide() override;
+  void OnShow() override;
 
   // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   scoped_ptr<ScopedKeepAlive> keep_alive_;
   scoped_ptr<NewWindowContentsDelegate> new_window_contents_delegate_;
   base::Closure terminating_callback_;
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeAppDelegate);
 };
 
 #endif  // CHROME_BROWSER_UI_APPS_CHROME_APP_DELEGATE_H_