Make win_aura work without ash.

ui/aura/root_window_host_linux.h

 // 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.
 
 #ifndef UI_AURA_ROOT_WINDOW_HOST_LINUX_H_
 #define UI_AURA_ROOT_WINDOW_HOST_LINUX_H_
 #pragma once
 
 #include <X11/Xlib.h>
 
@@ skipping 12 matching lines @@
  public:
   explicit RootWindowHostLinux(const gfx::Rect& bounds);
   virtual ~RootWindowHostLinux();
 
   // Overridden from Dispatcher overrides:
   virtual bool Dispatch(const base::NativeEvent& event) OVERRIDE;
 
  private:
   // RootWindowHost Overrides.
   virtual void SetRootWindow(RootWindow* root_window) OVERRIDE;
+  virtual RootWindow* GetRootWindow() OVERRIDE;
   virtual gfx::AcceleratedWidget GetAcceleratedWidget() OVERRIDE;
   virtual void Show() OVERRIDE;
   virtual void ToggleFullScreen() OVERRIDE;
   virtual gfx::Rect GetBounds() const OVERRIDE;
   virtual void SetBounds(const gfx::Rect& bounds) OVERRIDE;
   virtual gfx::Point GetLocationOnNativeScreen() const OVERRIDE;
   virtual void SetCapture() OVERRIDE;
   virtual void ReleaseCapture() OVERRIDE;
   virtual void SetCursor(gfx::NativeCursor cursor_type) OVERRIDE;
   virtual void ShowCursor(bool show) OVERRIDE;
@@ skipping 50 matching lines @@
   bool focus_when_shown_;
 
   scoped_array<XID> pointer_barriers_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowHostLinux);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ROOT_WINDOW_HOST_LINUX_H_