Demonstrate external-window-mode in mus-demo

services/ui/ws/window_server.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 "services/ui/ws/window_server.h"
 
 #include <set>
 #include <string>
 
 #include "base/logging.h"
@@ skipping 742 matching lines @@
   // The display compositor gets its own thread in mus-gpu. The gpu service,
   // where GL commands are processed resides on its own thread. Various
   // components of the display compositor such as Display, ResourceProvider,
   // and GLRenderer block on sync tokens from other command buffers. Thus,
   // the gpu service must live on a separate thread.
   gpu_proxy_->CreateDisplayCompositor(
       std::move(display_compositor_request_),
       display_compositor_client_binding_.CreateInterfacePtrAndBind());
   // TODO(kylechar): When gpu channel is removed, this can instead happen
   // earlier, after GpuServiceProxy::OnInitialized().
-  delegate_->StartDisplayInit();
+  bool window_manager_connected = false;
+  for (auto* factory : window_manager_window_tree_factory_set_.GetFactories()) {
+    if (factory->window_tree()) {
+      window_manager_connected = true;
+      break;
+    }
+  }
+  delegate_->StartDisplayInit(window_manager_connected);
 }
 
 void WindowServer::OnSurfaceCreated(const cc::SurfaceId& surface_id,
                                     const gfx::Size& frame_size,
                                     float device_scale_factor) {
   WindowId window_id(
       WindowIdFromTransportId(surface_id.frame_sink_id().client_id()));
   mojom::CompositorFrameSinkType compositor_frame_sink_type(
       static_cast<mojom::CompositorFrameSinkType>(
           surface_id.frame_sink_id().sink_id()));
@@ skipping 40 matching lines @@
 void WindowServer::OnUserIdAdded(const UserId& id) {
   activity_monitor_map_[id] = base::MakeUnique<UserActivityMonitor>(nullptr);
 }
 
 void WindowServer::OnUserIdRemoved(const UserId& id) {
   activity_monitor_map_.erase(id);
 }
 
 }  // namespace ws
 }  // namespace ui