Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/aura/test/aura_test_helper.cc

Index: ui/aura/test/aura_test_helper.cc
diff --git a/ui/aura/test/aura_test_helper.cc b/ui/aura/test/aura_test_helper.cc
index 73ab56a7ef69e23320517563f74f85723aee7248..d6db502db14fec076f0162b0348174fe00059113 100644
--- a/ui/aura/test/aura_test_helper.cc
+++ b/ui/aura/test/aura_test_helper.cc
@@ -10,9 +10,7 @@
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/focus_manager.h"
-#include "ui/aura/display_manager.h"
 #include "ui/aura/root_window.h"
-#include "ui/aura/single_display_manager.h"
 #include "ui/aura/test/test_activation_client.h"
 #include "ui/aura/test/test_screen.h"
 #include "ui/aura/test/test_stacking_client.h"
@@ -44,10 +42,10 @@ AuraTestHelper::~AuraTestHelper() {
 
 void AuraTestHelper::SetUp() {
   setup_called_ = true;
-  Env::GetInstance()->SetDisplayManager(new SingleDisplayManager);
-  root_window_.reset(aura::DisplayManager::CreateRootWindowForPrimaryDisplay());
-  test_screen_.reset(new aura::TestScreen(root_window_.get()));
+  aura::Env::GetInstance();
+  test_screen_.reset(new TestScreen());
   gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, test_screen_.get());
+  root_window_.reset(test_screen_->CreateRootWindowForPrimaryDisplay());
   ui_controls::InstallUIControlsAura(CreateUIControlsAura(root_window_.get()));
 
   focus_manager_.reset(new FocusManager);