chromeos: Eliminate WmWindow from //ash/system

ash/system/status_area_widget_delegate.cc

 // Copyright (c) 2012 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 "ash/system/status_area_widget_delegate.h"
 
 #include "ash/focus_cycler.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_controller.h"
 #include "ash/shelf/shelf_constants.h"
@@ skipping 86 matching lines @@
   return View::GetWidget();
 }
 
 const views::Widget* StatusAreaWidgetDelegate::GetWidget() const {
   return View::GetWidget();
 }
 
 void StatusAreaWidgetDelegate::OnGestureEvent(ui::GestureEvent* event) {
   views::Widget* target_widget =
       static_cast<views::View*>(event->target())->GetWidget();
-  WmWindow* target_window = WmWindow::Get(target_widget->GetNativeWindow());
-  WmShelf* shelf = target_window->GetRootWindowController()->GetShelf();
+  WmShelf* shelf = WmShelf::ForWindow(target_widget->GetNativeWindow());
   if (shelf->ProcessGestureEvent(*event))
     event->StopPropagation();
   else
     views::AccessiblePaneView::OnGestureEvent(event);
 }
 
 bool StatusAreaWidgetDelegate::CanActivate() const {
   // We don't want mouse clicks to activate us, but we need to allow
   // activation when the user is using the keyboard (FocusCycler).
   const FocusCycler* focus_cycler = focus_cycler_for_testing_
@@ skipping 98 matching lines @@
   child->SetBorder(
       views::CreateEmptyBorder(top_edge, left_edge, bottom_edge, right_edge));
 
   // Layout on |child| needs to be updated based on new border value before
   // displaying; otherwise |child| will be showing with old border size.
   // Fix for crbug.com/623438.
   child->Layout();
 }
 
 }  // namespace ash