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

ui/views/widget/tooltip_manager_aura.h

 // Copyright (c) 2011 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.
 
 #ifndef UI_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_
 #define UI_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_
 
 #include "base/compiler_specific.h"
 #include "base/strings/string16.h"
 #include "ui/gfx/point.h"
 #include "ui/views/widget/tooltip_manager.h"
 
 namespace aura {
-class RootWindow;
 class Window;
 }
 
 namespace gfx {
 class FontList;
 }
 
 namespace views {
 
 class Widget;
 
 // TooltipManager implementation for Aura.
 class TooltipManagerAura : public TooltipManager {
  public:
   TooltipManagerAura(aura::Window* window, Widget* widget);
   virtual ~TooltipManagerAura();
 
   // Returns the FontList used by all TooltipManagerAuras.
   static const gfx::FontList& GetDefaultFontList();
 
   // TooltipManager:
   virtual const gfx::FontList& GetFontList() const OVERRIDE;
   virtual void UpdateTooltip() OVERRIDE;
   virtual void TooltipTextChanged(View* view) OVERRIDE;
 
  private:
   View* GetViewUnderPoint(const gfx::Point& point);
   void UpdateTooltipForTarget(View* target,
                               const gfx::Point& point,
-                              aura::RootWindow* root_window);
+                              aura::Window* root_window);
 
   aura::Window* window_;
   Widget* widget_;
   string16 tooltip_text_;
 
   DISALLOW_COPY_AND_ASSIGN(TooltipManagerAura);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_