Make Task Manager sort more meaningful

chrome/browser/task_management/providers/web_contents/subframe_task.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_management/providers/web_contents/subframe_task.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/grit/generated_resources.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/render_frame_host.h"
@@ skipping 56 matching lines @@
 void SubframeTask::UpdateTitle() {
   // This will be called when the title changes on the WebContents's main frame,
   // but this Task represents other frames, so we don't care.
 }
 
 void SubframeTask::UpdateFavicon() {
   // This will be called when the favicon changes on the WebContents's main
   // frame, but this Task represents other frames, so we don't care.
 }
 
+Task* SubframeTask::GetParentTask() const {
+  return main_task_;
+}
+
 void SubframeTask::Activate() {
   // Activate the root task.
   main_task_->Activate();
 }
 
 }  // namespace task_management