Demonstrate external-window-mode in mus-demo

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index b589f61554d4d335f741ecd7f77f81022a9082f6..28b55665ba56c9926b7ec704704316a785384cec 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -753,7 +753,14 @@ void WindowServer::OnGpuChannelEstablished(
     display->platform_display()->OnGpuChannelEstablished(gpu_channel_);
   // TODO(kylechar): When gpu channel is removed, this can instead happen
   // earlier, after GpuServiceProxy::OnInitialized().
-  delegate_->StartDisplayInit();
+  bool window_manager_connected = false;

[rjkroege, 2016/11/24 00:58:28]

I would have thought that GetFactories().size() > 0 would be sufficient and
safer against races at start? Probably sky@ knows for sure.

[Tom (Use chromium acct), 2016/11/28 20:47:37]

In my testing, there's an initial factory even when no window manager gets
connected.
sky@ can you verify this change?

+  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,