Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/aura/bench/bench_main.cc

Index: ui/aura/bench/bench_main.cc
diff --git a/ui/aura/bench/bench_main.cc b/ui/aura/bench/bench_main.cc
index c15ece4404ed14e9d8b06820f2cf8de902ec5aca..6d255ecb8e6883b903af34323ecd1a80d72c3b77 100644
--- a/ui/aura/bench/bench_main.cc
+++ b/ui/aura/bench/bench_main.cc
@@ -13,10 +13,11 @@
 #include "third_party/khronos/GLES2/gl2.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/aura/client/default_capture_client.h"
+#include "ui/aura/display_util.h"
 #include "ui/aura/env.h"
 #include "ui/aura/focus_manager.h"
 #include "ui/aura/root_window.h"
-#include "ui/aura/single_display_manager.h"
+#include "ui/aura/test/test_screen.h"
 #include "ui/aura/window.h"
 #include "ui/base/hit_test.h"
 #include "ui/base/resource/resource_bundle.h"
@@ -297,11 +298,12 @@ int main(int argc, char** argv) {
 
   MessageLoop message_loop(MessageLoop::TYPE_UI);
   ui::CompositorTestSupport::Initialize();
-  aura::SingleDisplayManager* manager = new aura::SingleDisplayManager;
-  manager->set_use_fullscreen_host_window(true);
-  aura::Env::GetInstance()->SetDisplayManager(manager);
+  aura::Env::GetInstance();
+  aura::SetUseFullscreenHostWindow(true);
+  aura::TestScreen test_screen;
+  gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, &test_screen);
   scoped_ptr<aura::RootWindow> root_window(
-      aura::DisplayManager::CreateRootWindowForPrimaryDisplay());
+      test_screen.CreateRootWindowForPrimaryDisplay());
   aura::client::SetCaptureClient(
       root_window.get(),
       new aura::client::DefaultCaptureClient(root_window.get()));