mash: Migrate ScopedTargetRootWindow to //ash/common

ash/wm/window_positioner_unittest.cc

Index: ash/wm/window_positioner_unittest.cc
diff --git a/ash/wm/window_positioner_unittest.cc b/ash/wm/window_positioner_unittest.cc
index 325022411b10e08ff6667ecd75cd020ca1d1d842..3538962e4bbb4b77cb1c7b02c9cff4182ede55cc 100644
--- a/ash/wm/window_positioner_unittest.cc
+++ b/ash/wm/window_positioner_unittest.cc
@@ -7,16 +7,17 @@
 #include <string>
 
 #include "ash/common/material_design/material_design_controller.h"
+#include "ash/common/scoped_root_window_for_new_windows.h"
 #include "ash/common/wm/window_positioner.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/common/wm_shell.h"
+#include "ash/common/wm_window.h"
 #include "ash/shell.h"
 #include "ash/shell/toplevel_window.h"
 #include "ash/test/ash_md_test_base.h"
 #include "ash/test/test_shell_delegate.h"
 #include "ash/wm/window_state_aura.h"
 #include "base/strings/string_number_conversions.h"
-#include "ui/aura/window_event_dispatcher.h"
 #include "ui/display/screen.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
@@ -39,7 +40,8 @@ TEST_P(WindowPositionerTest, OpenMaximizedWindowOnSecondDisplay) {
   // Tests that for a screen that is narrower than kForceMaximizeWidthLimit
   // a new window gets maximized.
   UpdateDisplay("400x400,500x500");
-  Shell::GetInstance()->set_target_root_window(Shell::GetAllRootWindows()[1]);
+  ScopedRootWindowForNewWindows root_for_new_windows(
+      WmShell::Get()->GetAllRootWindows()[1]);
   shell::ToplevelWindow::CreateParams params;
   params.can_resize = true;
   params.can_maximize = true;
@@ -55,8 +57,8 @@ TEST_P(WindowPositionerTest, OpenDefaultWindowOnSecondDisplay) {
   ash::WindowPositioner::SetMaximizeFirstWindow(true);
 #endif
   UpdateDisplay("400x400,1400x900");
-  aura::Window* second_root_window = Shell::GetAllRootWindows()[1];
-  Shell::GetInstance()->set_target_root_window(second_root_window);
+  WmWindow* second_root_window = WmShell::Get()->GetAllRootWindows()[1];
+  ScopedRootWindowForNewWindows root_for_new_windows(second_root_window);
   shell::ToplevelWindow::CreateParams params;
   params.can_resize = true;
   params.can_maximize = true;
@@ -68,10 +70,9 @@ TEST_P(WindowPositionerTest, OpenDefaultWindowOnSecondDisplay) {
   // The window should be in the 2nd display with the default size.
   EXPECT_EQ("300x300", bounds.size().ToString());
 #endif
-  EXPECT_TRUE(display::Screen::GetScreen()
-                  ->GetDisplayNearestWindow(second_root_window)
-                  .bounds()
-                  .Contains(bounds));
+
+  EXPECT_TRUE(
+      second_root_window->GetDisplayNearestWindow().bounds().Contains(bounds));
 }
 
 // Tests that second window inherits first window's maximized state as well as