mash: Migrate ScopedTargetRootWindow to //ash/common

ash/mus/bridge/wm_shell_mus.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/mus/bridge/wm_shell_mus.h"
 
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
 #include "ash/common/display/display_info.h"
@@ skipping 137 matching lines @@
 }
 
 // static
 WmShellMus* WmShellMus::Get() {
   return static_cast<WmShellMus*>(WmShell::Get());
 }
 
 void WmShellMus::AddRootWindowController(
     WmRootWindowControllerMus* controller) {
   root_window_controllers_.push_back(controller);
+  // The first root window will be the initial root for new windows.
+  if (!GetRootWindowForNewWindows())
+    set_root_window_for_new_windows(controller->GetWindow());
 }
 
 void WmShellMus::RemoveRootWindowController(
     WmRootWindowControllerMus* controller) {
   auto iter = std::find(root_window_controllers_.begin(),
                         root_window_controllers_.end(), controller);
   DCHECK(iter != root_window_controllers_.end());
   root_window_controllers_.erase(iter);
 }
 
@@ skipping 31 matching lines @@
 }
 
 WmWindow* WmShellMus::GetPrimaryRootWindow() {
   return root_window_controllers_[0]->GetWindow();
 }
 
 WmWindow* WmShellMus::GetRootWindowForDisplayId(int64_t display_id) {
   return GetRootWindowControllerWithDisplayId(display_id)->GetWindow();
 }
 
-WmWindow* WmShellMus::GetRootWindowForNewWindows() {
-  NOTIMPLEMENTED();
-  return root_window_controllers_[0]->GetWindow();
-}
-
 const DisplayInfo& WmShellMus::GetDisplayInfo(int64_t display_id) const {
   NOTIMPLEMENTED();
   static DisplayInfo fake_info;
   return fake_info;
 }
 
 bool WmShellMus::IsActiveDisplayId(int64_t display_id) const {
   // TODO: implement http://crbug.com/622480.
   NOTIMPLEMENTED();
   return true;
@@ skipping 126 matching lines @@
 
 // static
 bool WmShellMus::IsActivationParent(ui::Window* window) {
   return window && IsActivatableShellWindowId(
                        WmWindowMus::Get(window)->GetShellWindowId());
 }
 
 // TODO: support OnAttemptToReactivateWindow, http://crbug.com/615114.
 void WmShellMus::OnWindowTreeFocusChanged(ui::Window* gained_focus,
                                           ui::Window* lost_focus) {
-  WmWindowMus* gained_active = GetToplevelAncestor(gained_focus);
-  WmWindowMus* lost_active = GetToplevelAncestor(gained_focus);
+  WmWindow* gained_active = GetToplevelAncestor(gained_focus);
+  if (gained_active)
+    set_root_window_for_new_windows(gained_active->GetRootWindow());
+
+  WmWindow* lost_active = GetToplevelAncestor(gained_focus);
   if (gained_active == lost_active)
     return;
 
   FOR_EACH_OBSERVER(WmActivationObserver, activation_observers_,
                     OnWindowActivated(gained_active, lost_active));
 }
 
 void WmShellMus::OnDidDestroyClient(ui::WindowTreeClient* client) {
   DCHECK_EQ(window_tree_client(), client);
   client->RemoveObserver(this);
 }
 
 }  // namespace mus
 }  // namespace ash