Add a "Keepalive count" column to Task Manager.

chrome/browser/task_manager/providers/web_contents/extension_task.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 CHROME_BROWSER_TASK_MANAGER_PROVIDERS_WEB_CONTENTS_EXTENSION_TASK_H_
 #define CHROME_BROWSER_TASK_MANAGER_PROVIDERS_WEB_CONTENTS_EXTENSION_TASK_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
 // Defines a task manager representation for extensions.
 class ExtensionTask
     : public RendererTask,
       public extensions::IconImage::Observer {
  public:
   ExtensionTask(content::WebContents* web_contents,
                 const extensions::Extension* extension,
                 extensions::ViewType view_type);
   ~ExtensionTask() override;
 
-  // task_manager::RendererTask:
+  // task_manager::RendererTask
   void UpdateTitle() override;
   void UpdateFavicon() override;
   void Activate() override;
   Type GetType() const override;
 
+  // task_manager::Task
+  int GetKeepaliveCount() const override;
+
   // extensions::IconImage::Observer
   void OnExtensionIconImageChanged(extensions::IconImage* image) override;
 
  private:
   // If |extension| is nullptr, this method will get the title from
   // the |web_contents|.
   base::string16 GetExtensionTitle(
       content::WebContents* web_contents,
       const extensions::Extension* extension,
       extensions::ViewType view_type) const;
 
   // This is called upon the creation of this task to load the extension icon
   // for the first time if any.
   void LoadExtensionIcon(const extensions::Extension* extension);
 
   // The favicon of the extension represented by this task.
   std::unique_ptr<extensions::IconImage> extension_icon_;
 
+  const extensions::ViewType view_type_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionTask);
 };
 
 }  // namespace task_manager
 
 #endif  // CHROME_BROWSER_TASK_MANAGER_PROVIDERS_WEB_CONTENTS_EXTENSION_TASK_H_