Moves maintaining root_window_for_new_windows_ to Shell

ash/magnifier/magnification_controller.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/magnifier/magnification_controller.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
@@ skipping 522 matching lines @@
   StartOrStopScrollIfNecessary();
 }
 
 void MagnificationControllerImpl::OnWindowDestroying(
     aura::Window* root_window) {
   if (root_window == root_window_) {
     // There must be at least one root window because this controller is
     // destroyed before the root windows get destroyed.
     DCHECK(root_window);
 
-    aura::Window* target_root_window = Shell::GetTargetRootWindow();
+    aura::Window* target_root_window = Shell::GetRootWindowForNewWindows();
     CHECK(target_root_window);
 
     // The destroyed root window must not be target.
     CHECK_NE(target_root_window, root_window);
     // Don't redraw the old root window as it's being destroyed.
     SwitchTargetRootWindow(target_root_window, false);
     point_of_interest_ = target_root_window->bounds().CenterPoint();
   }
 }
 
@@ skipping 332 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // MagnificationController:
 
 // static
 MagnificationController* MagnificationController::CreateInstance() {
   return new MagnificationControllerImpl();
 }
 
 }  // namespace ash