Converts WindowTreeClientTest to be in terms of aura

ash/mus/window_manager.cc

 // Copyright 2015 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/window_manager.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 324 matching lines @@
                  ->GetRootWindowController())
       ->root_window_controller();
 }
 
 void WindowManager::OnEmbed(
     std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
   // WindowManager should never see this, instead OnWmNewDisplay() is called.
   NOTREACHED();
 }
 
-void WindowManager::OnEmbedRootDestroyed(aura::Window* root) {
+void WindowManager::OnEmbedRootDestroyed(
+    aura::WindowTreeHostMus* window_tree_host) {
   // WindowManager should never see this.
   NOTREACHED();
 }
 
 void WindowManager::OnLostConnection(aura::WindowTreeClient* client) {
   DCHECK_EQ(client, window_tree_client_.get());
   Shutdown();
   // TODO(sky): this case should trigger shutting down WindowManagerApplication
   // too.
 }
@@ skipping 155 matching lines @@
 
 void WindowManager::OnWindowInitialized(aura::Window* window) {
   // This ensures WmWindowAura won't be called before WmWindowMus. This is
   // important as if WmWindowAura::Get() is called first, then WmWindowAura
   // would be created, not WmWindowMus.
   WmWindowMus::Get(window);
 }
 
 }  // namespace mus
 }  // namespace ash