Add a "Keepalive count" column to Task Manager.

chrome/browser/task_manager/sampling/task_manager_impl.cc

Index: chrome/browser/task_manager/sampling/task_manager_impl.cc
diff --git a/chrome/browser/task_manager/sampling/task_manager_impl.cc b/chrome/browser/task_manager/sampling/task_manager_impl.cc
index dfed65a971cf3fa535f373a53e1eb853cbfe5444..41c2d4457a477ecb0bd25eea7c18997b042606c8 100644
--- a/chrome/browser/task_manager/sampling/task_manager_impl.cc
+++ b/chrome/browser/task_manager/sampling/task_manager_impl.cc
@@ -273,6 +273,14 @@ bool TaskManagerImpl::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";