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

ash/wm/window_util.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/window_util.h"
 
 #include <vector>
 
 #include "ash/ash_constants.h"
 #include "ash/shell.h"
@@ skipping 82 matching lines @@
     bounds->set_y(min_height - bounds->height());
   }
   if (bounds->y() < 0)
     bounds->set_y(0);
 }
 
 bool MoveWindowToEventRoot(aura::Window* window, const ui::Event& event) {
   views::View* target = static_cast<views::View*>(event.target());
   if (!target)
     return false;
-  aura::RootWindow* target_root =
+  aura::Window* target_root =
       target->GetWidget()->GetNativeView()->GetRootWindow();
   if (!target_root || target_root == window->GetRootWindow())
     return false;
   aura::Window* window_container =
       ash::Shell::GetContainer(target_root, window->parent()->id());
   // Move the window to the target launcher.
   window_container->AddChild(window);
   return true;
 }
 
 void ReparentChildWithTransientChildren(aura::Window* window,
                                         aura::Window* child) {
   window->AddChild(child);
   ReparentTransientChildrenOfChild(window, child);
 }
 
 void ReparentTransientChildrenOfChild(aura::Window* window,
                                       aura::Window* child) {
   for (size_t i = 0; i < child->transient_children().size(); ++i)
     ReparentChildWithTransientChildren(window, child->transient_children()[i]);
 }
 
 }  // namespace wm
 }  // namespace ash