TaskManager: when shown or activated, select the last active tab.

chrome/browser/task_management/test_task_manager.cc

Index: chrome/browser/task_management/test_task_manager.cc
diff --git a/chrome/browser/task_management/test_task_manager.cc b/chrome/browser/task_management/test_task_manager.cc
index 79fd50e2ed073e67b90f3004da8e635124759b1c..5dc9e53eb5700be86454d5cdf94364d7743d1fc9 100644
--- a/chrome/browser/task_management/test_task_manager.cc
+++ b/chrome/browser/task_management/test_task_manager.cc
@@ -161,6 +161,11 @@ size_t TestTaskManager::GetNumberOfTasksOnSameProcess(TaskId task_id) const {
   return 1;
 }
 
+TaskId TestTaskManager::GetTaskIdForWebContents(
+    content::WebContents* web_contents) const {
+  return -1;
+}
+
 base::TimeDelta TestTaskManager::GetRefreshTime() {
   return GetCurrentRefreshTime();
 }