Make GetRootWindow() return a Window instead of a RootWindow.

ash/wm/workspace/workspace_layout_manager.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/wm/workspace/workspace_layout_manager.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shelf/shelf_layout_manager.h"
@@ skipping 37 matching lines @@
   // work area information like WindowResizer does for the
   // last window location.
   gfx::Rect display_area = Shell::GetScreen()->GetDisplayNearestWindow(
       window_state->window()).bounds();
 
   if (!display_area.Intersects(restore_bounds)) {
     DisplayController* display_controller =
         Shell::GetInstance()->display_controller();
     const gfx::Display& display =
         display_controller->GetDisplayMatching(restore_bounds);
-    aura::RootWindow* new_root =
+    aura::Window* new_root =
         display_controller->GetRootWindowForDisplayId(display.id());
     if (new_root != window_state->window()->GetRootWindow()) {
       aura::Window* new_container =
           Shell::GetContainer(new_root, window_state->window()->parent()->id());
       new_container->AddChild(window_state->window());
     }
   }
 }
 
 }  // namespace
@@ skipping 313 matching lines @@
         window_state->window(),
         ScreenAsh::GetDisplayBoundsInParent(
             window_state->window()->parent()->parent()));
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace ash