Ensure compositor initialized before WindowTreeHost is Shown.

ui/aura/mus/window_tree_client.cc

 // Copyright 2014 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/aura/mus/window_tree_client.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 381 matching lines @@
 std::unique_ptr<WindowTreeHostMus> WindowTreeClient::CreateWindowTreeHost(
     WindowMusType window_mus_type,
     const ui::mojom::WindowData& window_data,
     int64_t display_id) {
   std::unique_ptr<WindowPortMus> window_port =
       CreateWindowPortMus(window_data, window_mus_type);
   roots_.insert(window_port.get());
   std::unique_ptr<WindowTreeHostMus> window_tree_host =
       base::MakeUnique<WindowTreeHostMus>(std::move(window_port), this,
                                           display_id);
+  window_tree_host->InitHost();
   SetLocalPropertiesFromServerProperties(
       WindowMus::Get(window_tree_host->window()), window_data);
   if (window_data.visible) {
     SetWindowVisibleFromServer(WindowMus::Get(window_tree_host->window()),
                                true);
   }
   SetWindowBoundsFromServer(WindowMus::Get(window_tree_host->window()),
                             window_data.bounds);
   return window_tree_host;
 }
@@ skipping 1274 matching lines @@
   return ScheduleInFlightChange(base::MakeUnique<InFlightCaptureChange>(
       this, capture_synchronizer_.get(), window));
 }
 
 uint32_t WindowTreeClient::CreateChangeIdForFocus(WindowMus* window) {
   return ScheduleInFlightChange(base::MakeUnique<InFlightFocusChange>(
       this, focus_synchronizer_.get(), window));
 }
 
 }  // namespace aura