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

ash/wm/workspace/workspace_window_resizer.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_window_resizer.h"
 
 #include <algorithm>
 #include <cmath>
 #include <utility>
 #include <vector>
@@ skipping 372 matching lines @@
       if (!details_.restore_bounds.IsEmpty())
         window_state()->ClearRestoreBounds();
       RestackWindows();
     }
     did_move_or_resize_ = true;
   }
 
   gfx::Point location_in_screen = location_in_parent;
   wm::ConvertPointToScreen(window()->parent(), &location_in_screen);
 
-  aura::RootWindow* root = NULL;
+  aura::Window* root = NULL;
   gfx::Display display =
       ScreenAsh::FindDisplayContainingPoint(location_in_screen);
   // Track the last screen that the pointer was on to keep the snap phantom
   // window there.
   if (display.is_valid()) {
     root = Shell::GetInstance()->display_controller()->
         GetRootWindowForDisplayId(display.id());
   }
   if (!attached_windows_.empty())
     LayoutAttachedWindows(&bounds);
@@ skipping 600 matching lines @@
     if (!dock_layout_->is_dragged_window_docked())
       dock_layout_->DockDraggedWindow(window());
   } else {
     if (dock_layout_->is_dragged_window_docked())
       dock_layout_->UndockDraggedWindow();
   }
 }
 
 }  // namespace internal
 }  // namespace ash