Fix task manager table scrollbar issue.

chrome/browser/ui/task_manager/task_manager_table_model.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/ui/task_manager/task_manager_table_model.h"
 
 #include "base/command_line.h"
 #include "base/i18n/number_formatting.h"
 #include "base/i18n/rtl.h"
 #include "base/prefs/scoped_user_pref_update.h"
@@ skipping 566 matching lines @@
 void TaskManagerTableModel::OnTasksRefreshed(
     const TaskIdList& task_ids) {
   tasks_ = task_ids;
   OnRefresh();
 }
 
 void TaskManagerTableModel::StartUpdating() {
   TaskManagerInterface::GetTaskManager()->AddObserver(this);
   tasks_ = observed_task_manager()->GetTaskIdsList();
   OnRefresh();
+
+  // In order for the scrollbar of the TableView to work properly on startup of
+  // the task manager, we must invoke TableModelObserver::OnModelChanged() which
+  // in turn will invoke TableView::NumRowsChanged(). This will adjust the
+  // vertical scrollbar correctly. crbug.com/570966.
+  if (table_model_observer_)
+    table_model_observer_->OnModelChanged();
 }
 
 void TaskManagerTableModel::StopUpdating() {
   observed_task_manager()->RemoveObserver(this);
 }
 
 void TaskManagerTableModel::ActivateTask(int row_index) {
   observed_task_manager()->ActivateTask(tasks_[row_index]);
 }
 
@@ skipping 205 matching lines @@
 bool TaskManagerTableModel::IsTaskFirstInGroup(int row_index) const {
   if (row_index == 0)
     return true;
 
   return observed_task_manager()->GetProcessId(tasks_[row_index - 1]) !=
       observed_task_manager()->GetProcessId(tasks_[row_index]);
 }
 
 
 }  // namespace task_management