Converts WindowTreeClientTest to be in terms of aura

mash/simple_wm/simple_wm.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/simple_wm/simple_wm.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/display/screen_base.h"
 #include "ui/gfx/canvas.h"
@@ skipping 96 matching lines @@
   // WindowTreeClients configured as the window manager should never get
   // OnEmbed().
   NOTREACHED();
 }
 
 void SimpleWM::OnLostConnection(aura::WindowTreeClient* client) {
   window_tree_host_.reset();
   window_tree_client_.reset();
 }
 
-void SimpleWM::OnEmbedRootDestroyed(aura::Window* root) {
+void SimpleWM::OnEmbedRootDestroyed(aura::WindowTreeHostMus* window_tree_host) {
   // WindowTreeClients configured as the window manager should never get
   // OnEmbedRootDestroyed().
   NOTREACHED();
 }
 
 void SimpleWM::OnPointerEventObserved(const ui::PointerEvent& event,
                                       aura::Window* target) {
   // Don't care.
 }
 
@@ skipping 108 matching lines @@
     const std::vector<gfx::Rect>& additional_client_areas) {}
 
 SimpleWM::FrameView* SimpleWM::GetFrameViewForClientWindow(
     aura::Window* client_window) {
   auto it = client_window_to_frame_view_.find(client_window);
   return it != client_window_to_frame_view_.end() ? it->second : nullptr;
 }
 
 }  // namespace simple_wm