Removes a couple more functions from WmWindow

ash/mus/top_level_window_factory.cc

 // Copyright 2017 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/top_level_window_factory.h"
 
 #include "ash/mus/disconnected_app_handler.h"
 #include "ash/mus/frame/detached_title_area_renderer.h"
 #include "ash/mus/non_client_frame_controller.h"
 #include "ash/mus/property_util.h"
@@ skipping 113 matching lines @@
     WindowManager* window_manager,
     RootWindowController* root_window_controller,
     ui::mojom::WindowType window_type,
     std::map<std::string, std::vector<uint8_t>>* properties) {
   // TODO(sky): constrain and validate properties.
 
   int32_t container_id = kShellWindowId_Invalid;
   aura::Window* context = nullptr;
   aura::Window* container_window = nullptr;
   if (GetInitialContainerId(*properties, &container_id)) {
-    container_window = root_window_controller->GetWindow()
-                           ->GetChildByShellWindowId(container_id)
-                           ->aura_window();
+    container_window =
+        root_window_controller->GetRootWindow()->GetChildById(container_id);
   } else {
     context = root_window_controller->GetRootWindow();
   }
 
   gfx::Rect bounds = CalculateDefaultBounds(
       window_manager, root_window_controller, container_window, properties);
 
   const bool provide_non_client_frame =
       window_type == ui::mojom::WindowType::WINDOW ||
       window_type == ui::mojom::WindowType::PANEL;
   if (provide_non_client_frame) {
     // See NonClientFrameController for details on lifetime.
     NonClientFrameController* non_client_frame_controller =
         new NonClientFrameController(container_window, context, bounds,
                                      window_type, properties, window_manager);
     return non_client_frame_controller->window();
   }
 
   aura::PropertyConverter* property_converter =
       window_manager->property_converter();
 
   if (window_type == ui::mojom::WindowType::POPUP &&
       ShouldRenderTitleArea(property_converter, *properties)) {
     // Pick a parent so display information is obtained. Will pick the real one
     // once transient parent found.
     aura::Window* unparented_control_container =
-        root_window_controller->GetWindow()
-            ->GetChildByShellWindowId(kShellWindowId_UnparentedControlContainer)
-            ->aura_window();
+        root_window_controller->GetRootWindow()->GetChildById(
+            kShellWindowId_UnparentedControlContainer);
     // DetachedTitleAreaRendererForClient is owned by the client.
     DetachedTitleAreaRendererForClient* renderer =
         new DetachedTitleAreaRendererForClient(unparented_control_container,
                                                properties, window_manager);
     return renderer->widget()->GetNativeView();
   }
 
   aura::Window* window = new aura::Window(nullptr);
   aura::SetWindowType(window, window_type);
   window->SetProperty(aura::client::kEmbedType,
@@ skipping 52 matching lines @@
     if (non_client_frame_controller)
       non_client_frame_controller->set_can_activate(can_focus);
     // No need to persist this value.
     properties->erase(focusable_iter);
   }
   return window;
 }
 
 }  // namespace mus
 }  // namespace ash