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

services/ui/demo/window_tree_data.h

Index: services/ui/demo/window_tree_data.h
diff --git a/services/ui/demo/window_tree_data.h b/services/ui/demo/window_tree_data.h
index 007b04f6d284c4d87c9775f239c2a8c65562e9c3..a31d9b485a5ed3aa2c93f201e76fad2a69de100a 100644
--- a/services/ui/demo/window_tree_data.h
+++ b/services/ui/demo/window_tree_data.h
@@ -27,12 +27,18 @@ class WindowTreeData {
 
   // Initializes the window tree host and start drawing frames.
   void Init(std::unique_ptr<aura::WindowTreeHostMus> window_tree_host);
-  bool IsInitialized() const { return !!window_tree_host_; }
+  bool IsInitialized() const { return window_delegate_; }
 
   const aura::WindowTreeHostMus* WindowTreeHost() const {
     return window_tree_host_.get();
   }
 
+ protected:
+  void SetWindowTreeHost(
+      std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
+    window_tree_host_ = std::move(window_tree_host);
+  }
+
  private:
   // Draws one frame, incrementing the rotation angle.
   void DrawFrame();