Add a "Keepalive count" column to Task Manager.

chrome/browser/task_manager/sampling/task_manager_impl.cc

 // 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.
 
 #include "chrome/browser/task_manager/sampling/task_manager_impl.h"
 
 #include <algorithm>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
@@ skipping 255 matching lines @@
     blink::WebCache::ResourceTypeStats* stats) const {
   const Task* task = GetTaskByTaskId(task_id);
   if (!task->ReportsWebCacheStats())
     return false;
 
   *stats = task->GetWebCacheStats();
 
   return true;
 }
 
+int TaskManagerImpl::GetKeepaliveCount(TaskId task_id) const {
+  const Task* task = GetTaskByTaskId(task_id);
+  if (!task)
+    return -1;
+
+  return task->GetKeepaliveCount();
+}
+
 const TaskIdList& TaskManagerImpl::GetTaskIdsList() const {
   DCHECK(is_running_) << "Task manager is not running. You must observe the "
       "task manager for it to start running";
 
   if (sorted_task_ids_.empty()) {
     // |comparator| groups and sorts by subtask-ness (to push all subtasks to be
     // last), then by process type (e.g. the browser process should be first;
     // renderer processes should be together), then tab id (processes used by
     // the same tab should be kept together, and a tab should have a stable
     // position in the list as it cycles through processes, and tab creation
@@ skipping 276 matching lines @@
         groups_itr.second->AreBackgroundCalculationsDone();
   }
   if (are_all_processes_data_ready) {
     NotifyObserversOnRefreshWithBackgroundCalculations(GetTaskIdsList());
     for (const auto& groups_itr : task_groups_by_proc_id_)
       groups_itr.second->ClearCurrentBackgroundCalculationsFlags();
   }
 }
 
 }  // namespace task_manager