c++ / mojo changes for 'external window mode'

services/ui/demo/window_tree_data.cc

Index: services/ui/demo/window_tree_data.cc
diff --git a/services/ui/demo/window_tree_data.cc b/services/ui/demo/window_tree_data.cc
index 3d78c94df668343d7eb38d73ca32305ff5fd923c..65055a8a6dfe65f1b10cba3f2f625bbb9d0fcde5 100644
--- a/services/ui/demo/window_tree_data.cc
+++ b/services/ui/demo/window_tree_data.cc
@@ -68,10 +68,11 @@ aura::Window* WindowTreeData::bitmap_window() {
 
 void WindowTreeData::Init(
     std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
-  window_tree_host->InitHost();
-  window_tree_host->Show();
-  // Take ownership of the WTH.
-  window_tree_host_ = std::move(window_tree_host);
+  if (window_tree_host) {
+    window_tree_host->InitHost();
+    window_tree_host->Show();
+    SetWindowTreeHost(std::move(window_tree_host));
+  }
 
   // Initialize the window for the bitmap.
   window_delegate_ = new aura_extra::ImageWindowDelegate();