Refactor screen/monitor so that gfx::Screen returns monitor object.

ui/views/widget/native_widget_aura_unittest.cc

Index: ui/views/widget/native_widget_aura_unittest.cc
diff --git a/ui/views/widget/native_widget_aura_unittest.cc b/ui/views/widget/native_widget_aura_unittest.cc
index 51d4bc94391a2e3a5d37759065ef5f703fde7f28..84fc2aa49476736fc58f3a7f41e1a45e4aadabf4 100644
--- a/ui/views/widget/native_widget_aura_unittest.cc
+++ b/ui/views/widget/native_widget_aura_unittest.cc
@@ -13,15 +13,13 @@
 #include "ui/aura/monitor_manager.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/single_monitor_manager.h"
+#include "ui/aura/test/test_screen.h"
 #include "ui/aura/test/test_stacking_client.h"
 #include "ui/aura/window.h"
+#include "ui/gfx/screen.h"
 #include "ui/views/widget/root_view.h"
 #include "ui/views/widget/widget_delegate.h"
 
-#if defined(USE_ASH)
-#include "ui/aura/test/test_screen.h"
-#endif
-
 namespace views {
 namespace {
 
@@ -43,9 +41,7 @@ class NativeWidgetAuraTest : public testing::Test {
     aura::Env::GetInstance()->SetMonitorManager(new aura::SingleMonitorManager);
     root_window_.reset(
         aura::MonitorManager::CreateRootWindowForPrimaryMonitor());
-#if defined(USE_ASH)
     gfx::Screen::SetInstance(new aura::TestScreen(root_window_.get()));
-#endif
     root_window_->SetBounds(gfx::Rect(0, 0, 640, 480));
     root_window_->SetHostSize(gfx::Size(640, 480));
     test_stacking_client_.reset(