Add a "Keepalive count" column to Task Manager.

chrome/browser/task_manager/sampling/task_manager_impl.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_SAMPLING_TASK_MANAGER_IMPL_H_
 #define CHROME_BROWSER_TASK_MANAGER_SAMPLING_TASK_MANAGER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 67 matching lines @@
                             int* out_error_code) const override;
   int64_t GetNetworkUsage(TaskId task_id) const override;
   int64_t GetProcessTotalNetworkUsage(TaskId task_id) const override;
   int64_t GetSqliteMemoryUsed(TaskId task_id) const override;
   bool GetV8Memory(TaskId task_id,
                    int64_t* allocated,
                    int64_t* used) const override;
   bool GetWebCacheStats(
       TaskId task_id,
       blink::WebCache::ResourceTypeStats* stats) const override;
+  int GetKeepaliveCount(TaskId task_id) const override;
   const TaskIdList& GetTaskIdsList() const override;
   TaskIdList GetIdsOfTasksSharingSameProcess(TaskId task_id) const override;
   size_t GetNumberOfTasksOnSameProcess(TaskId task_id) const override;
   TaskId GetTaskIdForWebContents(
       content::WebContents* web_contents) const override;
 
   // task_manager::TaskProviderObserver:
   void TaskAdded(Task* task) override;
   void TaskRemoved(Task* task) override;
   void TaskUnresponsive(Task* task) override;
@@ skipping 70 matching lines @@
   // This will be set to true while there are observers and the task manager is
   // running.
   bool is_running_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskManagerImpl);
 };
 
 }  // namespace task_manager
 
 #endif  // CHROME_BROWSER_TASK_MANAGER_SAMPLING_TASK_MANAGER_IMPL_H_