Make Task Manager sort more meaningful

chrome/browser/task_management/task_manager_observer.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_MANAGEMENT_TASK_MANAGER_OBSERVER_H_
 #define CHROME_BROWSER_TASK_MANAGEMENT_TASK_MANAGER_OBSERVER_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 55 matching lines @@
   // resources than those defined in |resources_flags|.
   // 4- Upon the removal of the observer from the task manager, the task manager
   // will update its refresh time and the calculated resources to be the minimum
   // required value of all the remaining observers.
   TaskManagerObserver(base::TimeDelta refresh_time, int64_t resources_flags);
   virtual ~TaskManagerObserver();
 
   // Notifies the observer that a chrome task with |id| has started and the task
   // manager is now monitoring it. The resource usage of this newly-added task
   // will remain invalid until the next refresh cycle of the task manager.
-  virtual void OnTaskAdded(TaskId id) = 0;
+  virtual void OnTaskAdded(TaskId id) {}
 
   // Notifies the observer that a chrome task with |id| is about to be destroyed
   // and removed from the task manager right after this call. Observers which
   // are interested in doing some calculations related to the resource usage of
   // this task upon its removal may do so inside this call.
-  virtual void OnTaskToBeRemoved(TaskId id) = 0;
+  virtual void OnTaskToBeRemoved(TaskId id) {}
 
   // Notifies the observer that the task manager has just finished a refresh
   // cycle to calculate the resources usage of all tasks whose IDs are given in
   // |task_ids|. |task_ids| will be sorted such that the task representing the
   // browser process is at the top of the list and the rest of the IDs will be
   // sorted by the process IDs on which the tasks are running, then by the task
   // IDs themselves.
-  virtual void OnTasksRefreshed(const TaskIdList& task_ids) = 0;
+  virtual void OnTasksRefreshed(const TaskIdList& task_ids) {}
 
   // Notifies the observer that the task manager has just finished a refresh
   // cycle that calculated all the resource usage of all tasks whose IDs are in
   // |task_ids| including the resource usages that are calculated in the
   // background such CPU and memory (If those refresh types are enabled).
   // This event can take longer to be fired, and can miss some changes that may
   // happen to non-background calculations in-between two successive
   // invocations. Listen to this ONLY if you must know when all the background
   // resource calculations to be valid for all the available processes.
   // |task_ids| will be sorted as specified in OnTasksRefreshed() above.
@@ skipping 34 matching lines @@
   // calculated on each refresh.
   int64_t desired_resources_flags_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskManagerObserver);
 };
 
 }  // namespace task_management
 
 
 #endif  // CHROME_BROWSER_TASK_MANAGEMENT_TASK_MANAGER_OBSERVER_H_