chrome::ShowTaskManager: refine return type to eliminate a downcast.

chrome/browser/ui/views/browser_dialogs_views.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/browser_dialogs.h"
 
 #include <memory>
 
 #include "chrome/browser/chooser_controller/chooser_controller.h"
 #include "chrome/browser/extensions/api/chrome_device_permissions_prompt.h"
@@ skipping 38 matching lines @@
   ShowDialogViews();
 }
 
 void ChromeExtensionChooserDialog::ShowDialog(
     std::unique_ptr<ChooserController> chooser_controller) const {
   ShowDialogImpl(std::move(chooser_controller));
 }
 
 namespace chrome {
 
-ui::TableModel* ShowTaskManager(Browser* browser) {
+task_management::TaskManagerTableModel* ShowTaskManager(Browser* browser) {
   return task_management::NewTaskManagerView::Show(browser);
 }
 
 void HideTaskManager() {
   task_management::NewTaskManagerView::Hide();
 }
 
 bool NotifyOldTaskManagerBytesRead(const net::URLRequest& request,
                                    int64_t bytes_read) {
   return false;
 }
 
 }  // namespace chrome
 
 #if defined(OS_CHROMEOS)
 
 BubbleShowPtr ShowIntentPickerBubble() {
   return IntentPickerBubbleView::ShowBubble;
 }
 
 #endif  // OS_CHROMEOS