Aura on Linux: Make a DesktopScreenX11 to match the windows one.

chrome/browser/chrome_browser_main_extra_parts_aura.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 "chrome/browser/chrome_browser_main_extra_parts_aura.h"
 
 #include "ui/aura/env.h"
 
 #if !defined(USE_ASH)
+#include "ui/aura/desktop/desktop_screen.h"
 #include "ui/aura/desktop/desktop_stacking_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/single_monitor_manager.h"
+#include "ui/gfx/screen.h"
 #include "ui/views/widget/native_widget_aura.h"
 #endif  // !USE_ASH
 
 ChromeBrowserMainExtraPartsAura::ChromeBrowserMainExtraPartsAura()
     : ChromeBrowserMainExtraParts() {
 }
 
 void ChromeBrowserMainExtraPartsAura::PreProfileInit() {
 #if !defined(USE_ASH)
+  gfx::Screen::SetInstance(aura::CreateDesktopScreen());
   aura::Env::GetInstance()->SetMonitorManager(new aura::SingleMonitorManager);
   stacking_client_.reset(new aura::DesktopStackingClient);
 #endif  // !USE_ASH
 }
 
 void ChromeBrowserMainExtraPartsAura::PostMainMessageLoopRun() {
 #if !defined(USE_ASH)
   stacking_client_.reset();
 #endif
 
   // aura::Env instance is deleted in BrowserProcessImpl::StartTearDown
   // after the metrics service is deleted.
 }