Add an arbitrary delay before unloading lazy background pages.

chrome/browser/extensions/extension_process_manager.h

 // Copyright (c) 2012 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_EXTENSIONS_EXTENSION_PROCESS_MANAGER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_PROCESS_MANAGER_H_
 #pragma once
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "content/public/common/view_type.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class Browser;
 class Extension;
 class ExtensionHost;
 class GURL;
 class Profile;
 
@@ skipping 150 matching lines @@
 
   // Close the given |host| iff it's a background page.
   void CloseBackgroundHost(ExtensionHost* host);
 
   // Ensure browser object is not null except for certain situations.
   void EnsureBrowserWhenRequired(Browser* browser,
                                  content::ViewType view_type);
 
   // These are called when the extension transitions between idle and active.
   // They control the process of closing the background page when idle.
-  void OnLazyBackgroundPageIdle(const std::string& extension_id);
+  void OnLazyBackgroundPageIdle(const std::string& extension_id,
+                                int close_sequence_id);
   void OnLazyBackgroundPageActive(const std::string& extension_id);
 
   // Updates a potentially-registered RenderViewHost once it has been
   // associated with a WebContents. This allows us to gather information that
   // was not available when the host was first registered.
   void UpdateRegisteredRenderView(content::RenderViewHost* render_view_host);
 
   BackgroundPageDataMap background_page_data_;
 
+  base::WeakPtrFactory<ExtensionProcessManager> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionProcessManager);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_PROCESS_MANAGER_H_