aura-mus: Implement stacking in DesktopWindowTreeHostMus.

ui/views/mus/desktop_window_tree_host_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 "ui/views/mus/desktop_window_tree_host_mus.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
@@ skipping 386 matching lines @@
   screen_bounds.set_size(size);
   SetBoundsInDIP(screen_bounds);
 }
 
 void DesktopWindowTreeHostMus::StackAbove(aura::Window* window) {
   // TODO: implement window stacking, http://crbug.com/663617.
   NOTIMPLEMENTED();
 }
 
 void DesktopWindowTreeHostMus::StackAtTop() {
-  // TODO: implement window stacking, http://crbug.com/663617.
-  NOTIMPLEMENTED();
+  // Request to the server to stack our current mus window at the top. Our
+  // window() is a root, and we can't reach up past it so we can't just request
+  // a Reorder(), which is what we'd do to reorder our own subwindows.
+  WindowTreeHostMus::StackAtTop();
 }
 
 void DesktopWindowTreeHostMus::CenterWindow(const gfx::Size& size) {
   gfx::Rect bounds_to_center_in = GetWorkAreaBoundsInScreen();
 
   // If there is a transient parent and it fits |size|, then center over it.
   aura::Window* content_window = desktop_native_widget_aura_->content_window();
   if (wm::GetTransientParent(content_window)) {
     gfx::Rect transient_parent_bounds =
         wm::GetTransientParent(content_window)->GetBoundsInScreen();
@@ skipping 309 matching lines @@
     aura::client::FocusClient* focus_client,
     aura::Window* window) {
   if (window == this->window()) {
     desktop_native_widget_aura_->HandleActivationChanged(true);
   } else if (is_active_) {
     desktop_native_widget_aura_->HandleActivationChanged(false);
   }
 }
 
 }  // namespace views