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

ash/autoclick/autoclick_unittest.cc

 // Copyright 2013 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/autoclick/autoclick_controller.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
+#include "ui/aura/root_window.h"
 #include "ui/aura/test/event_generator.h"
 #include "ui/aura/window.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_handler.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 
 namespace ash {
 
 class MouseEventCapturer : public ui::EventHandler {
@@ skipping 234 matching lines @@
   generator2.MoveMouseTo(300, 400);
   events = WaitForMouseEvents();
   EXPECT_EQ(2u, events.size());
   EXPECT_EQ(300, events[0].root_location().x());
   EXPECT_EQ(400, events[0].root_location().y());
 
   // Test movement threshold between displays.
 }
 
 }  // namespace ash