Move gtk-specific browser main parts stuff to its own file.

chrome/browser/ui/views/chrome_browser_main_extra_parts_views.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/ui/views/chrome_browser_main_extra_parts_views.h"
 
 #include "chrome/browser/ui/views/chrome_constrained_window_views_client.h"
 #include "chrome/browser/ui/views/chrome_views_delegate.h"
 #include "components/constrained_window/constrained_window_views.h"
 
 #if defined(USE_AURA)
+#include "ui/gfx/screen.h"
+#include "ui/views/widget/desktop_aura/desktop_screen.h"
 #include "ui/wm/core/wm_state.h"
 #endif
 
 ChromeBrowserMainExtraPartsViews::ChromeBrowserMainExtraPartsViews() {
 }
 
 ChromeBrowserMainExtraPartsViews::~ChromeBrowserMainExtraPartsViews() {
   constrained_window::SetConstrainedWindowViewsClient(nullptr);
 }
 
 void ChromeBrowserMainExtraPartsViews::ToolkitInitialized() {
   // The delegate needs to be set before any UI is created so that windows
   // display the correct icon.
   if (!views::ViewsDelegate::GetInstance())
     views_delegate_.reset(new ChromeViewsDelegate);
 
   SetConstrainedWindowViewsClient(CreateChromeConstrainedWindowViewsClient());
 
 #if defined(USE_AURA)
   wm_state_.reset(new wm::WMState);
 #endif
 }
+
+void ChromeBrowserMainExtraPartsViews::PreCreateThreads() {
+#if defined(USE_AURA) && !defined(OS_CHROMEOS)
+  gfx::Screen::SetScreenInstance(views::CreateDesktopScreen());
+#endif
+}