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

chrome/browser/ui/views/browser_dialogs_views_mac.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 <utility>
 
 #include "chrome/browser/ui/bookmarks/bookmark_bubble_sign_in_delegate.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #include "chrome/browser/ui/views/bookmarks/bookmark_bubble_view.h"
@@ skipping 38 matching lines @@
                                     bool already_bookmarked) {
   // The Views dialog may prompt for sign in.
   std::unique_ptr<BubbleSyncPromoDelegate> delegate(
       new BookmarkBubbleSignInDelegate(browser));
 
   BookmarkBubbleView::ShowBubble(
       nullptr, gfx::Rect(anchor_point, gfx::Size()), parent, observer,
       std::move(delegate), browser->profile(), virtual_url, already_bookmarked);
 }
 
-ui::TableModel* ShowTaskManagerViews(Browser* browser) {
+task_management::TaskManagerTableModel* ShowTaskManagerViews(Browser* browser) {
   // On platforms other than Mac, the new task manager is shown unless
   // explicitly disabled. Assume that running with ToolkitViewsDialogsEnabled()
   // on Mac also means the new task manager is desired.
   return task_management::NewTaskManagerView::Show(browser);
 }
 
 void HideTaskManagerViews() {
   task_management::NewTaskManagerView::Hide();
 }
 
 void ContentSettingBubbleViewsBridge::Show(gfx::NativeView parent_view,
                                            ContentSettingBubbleModel* model,
                                            content::WebContents* web_contents,
                                            const gfx::Point& anchor) {
   ContentSettingBubbleContents* contents =
       new ContentSettingBubbleContents(model, web_contents, nullptr,
           views::BubbleBorder::Arrow::TOP_RIGHT);
   contents->set_parent_window(parent_view);
   contents->SetAnchorRect(gfx::Rect(anchor, gfx::Size()));
   views::BubbleDialogDelegateView::CreateBubble(contents)->Show();
 }
 
 }  // namespace chrome