Add a "Keepalive count" column to Task Manager.

chrome/browser/task_manager/providers/task.cc

Index: chrome/browser/task_manager/providers/task.cc
diff --git a/chrome/browser/task_manager/providers/task.cc b/chrome/browser/task_manager/providers/task.cc
index 82d8656caf173fc9dea4c95940fe2abced949249..a49032f6875cd6612cc2777b5606b34ff56d9356 100644
--- a/chrome/browser/task_manager/providers/task.cc
+++ b/chrome/browser/task_manager/providers/task.cc
@@ -143,6 +143,10 @@ blink::WebCache::ResourceTypeStats Task::GetWebCacheStats() const {
   return blink::WebCache::ResourceTypeStats();
 }
 
+int Task::GetKeepaliveCount() const {
+  return -1;
+}
+
 bool Task::ReportsNetworkUsage() const {
   return network_usage_ != -1;
 }