mash: Migrate ScopedTargetRootWindow to //ash/common

ash/common/wm_shell.cc

 // Copyright 2016 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 "ash/common/wm_shell.h"
 
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
 #include "ash/common/accelerators/ash_focus_manager_factory.h"
@@ skipping 126 matching lines @@
       window_cycle_controller_(new WindowCycleController),
       window_selector_controller_(new WindowSelectorController) {
 #if defined(OS_CHROMEOS)
   brightness_control_delegate_.reset(new system::BrightnessControllerChromeos);
   keyboard_brightness_control_delegate_.reset(new KeyboardBrightnessController);
 #endif
 }
 
 WmShell::~WmShell() {}
 
+WmWindow* WmShell::GetRootWindowForNewWindows() {
+  if (scoped_root_window_for_new_windows_)
+    return scoped_root_window_for_new_windows_;
+  return root_window_for_new_windows_;
+}
+
 bool WmShell::IsSystemModalWindowOpen() {
   if (simulate_modal_window_open_for_testing_)
     return true;
 
   // Traverse all system modal containers, and find its direct child window
   // with "SystemModal" setting, and visible.
   for (WmWindow* root : GetAllRootWindows()) {
     WmWindow* system_modal =
         root->GetChildByShellWindowId(kShellWindowId_SystemModalContainer);
     if (!system_modal)
@@ skipping 98 matching lines @@
 void WmShell::DeleteToastManager() {
   toast_manager_.reset();
 }
 
 void WmShell::SetAcceleratorController(
     std::unique_ptr<AcceleratorController> accelerator_controller) {
   accelerator_controller_ = std::move(accelerator_controller);
 }
 
 }  // namespace ash