Makes RootWindowController window creation in terms of common types

mash/wm/root_window_controller.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 "mash/wm/root_window_controller.h"
 
 #include <stdint.h>
 
 #include <map>
 #include <sstream>
@@ skipping 302 matching lines @@
   layout_managers_[status].reset(new StatusLayoutManager(status));
 
   mus::Window* user_private_windows =
       GetWindowForContainer(mojom::Container::USER_PRIVATE_WINDOWS);
   // WorkspaceLayoutManager is not a mash::wm::LayoutManager (it's an
   // ash::wm::LayoutManager), so it can't be in |layout_managers_|.
   layout_managers_.erase(user_private_windows);
   std::unique_ptr<WorkspaceLayoutManagerDelegateImpl>
       workspace_layout_manager_delegate(new WorkspaceLayoutManagerDelegateImpl(
           wm_root_window_controller_.get()));
-  WmWindowMus::Get(user_private_windows)
-      ->SetLayoutManager(base::WrapUnique(new ash::WorkspaceLayoutManager(
-          WmWindowMus::Get(user_private_windows),
+  WmWindowMus* user_private_windows_wm = WmWindowMus::Get(user_private_windows);
+  user_private_windows_wm->SetSnapsChildrenToPhysicalPixelBoundary();
+  user_private_windows_wm->SetChildrenUseExtendedHitRegion();
+  user_private_windows_wm->SetLayoutManager(
+      base::WrapUnique(new ash::WorkspaceLayoutManager(
+          user_private_windows_wm,
           std::move(workspace_layout_manager_delegate))));
 
   mus::Window* user_private_docked_windows =
       GetWindowForContainer(mojom::Container::USER_PRIVATE_DOCKED_WINDOWS);
   WmWindowMus* user_private_docked_windows_wm =
       WmWindowMus::Get(user_private_docked_windows);
+  user_private_docked_windows_wm->SetSnapsChildrenToPhysicalPixelBoundary();
   layout_managers_.erase(user_private_docked_windows);
+  user_private_docked_windows_wm->SetChildrenUseExtendedHitRegion();
   user_private_docked_windows_wm->SetLayoutManager(base::WrapUnique(
       new ash::DockedWindowLayoutManager(user_private_docked_windows_wm)));
 
   mus::Window* user_private_panels =
       GetWindowForContainer(mojom::Container::USER_PRIVATE_PANELS);
   WmWindowMus* user_private_panels_wm = WmWindowMus::Get(user_private_panels);
+  user_private_panels_wm->SetSnapsChildrenToPhysicalPixelBoundary();
   layout_managers_.erase(user_private_panels);
+  user_private_panels_wm->SetChildrenUseExtendedHitRegion();
   user_private_panels_wm->SetLayoutManager(
       base::WrapUnique(new ash::PanelLayoutManager(user_private_panels_wm)));
+
+  mus::Window* user_private_always_on_top = GetWindowForContainer(
+      mojom::Container::USER_PRIVATE_ALWAYS_ON_TOP_WINDOWS);
+  WmWindowMus* user_private_always_on_top_wm =
+      WmWindowMus::Get(user_private_always_on_top);
+  user_private_always_on_top_wm->SetChildrenUseExtendedHitRegion();
+  user_private_always_on_top_wm->SetSnapsChildrenToPhysicalPixelBoundary();
 }
 
 }  // namespace wm
 }  // namespace mash