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

services/ui/ws/display.h

Index: services/ui/ws/display.h
diff --git a/services/ui/ws/display.h b/services/ui/ws/display.h
index 478f16a37a93e48de6cf96cb6940865af3e22bd2..f1d28f36e05b77aea94a675b2273fb8cd0188a3b 100644
--- a/services/ui/ws/display.h
+++ b/services/ui/ws/display.h
@@ -153,7 +153,11 @@ class Display : public PlatformDisplayDelegate,
   using WindowManagerDisplayRootMap =
       std::map<UserId, WindowManagerDisplayRoot*>;
 
-  // Inits the necessary state once the display is ready.
+  // Inits the display root once the display is ready in
+  // 'external window mode'.
+  void InitDisplayRoot();
+
+  // Inits the necessary WindowManager state once the display is ready.
   void InitWindowManagerDisplayRoots();
 
   // Creates the set of WindowManagerDisplayRoots from the
@@ -207,6 +211,8 @@ class Display : public PlatformDisplayDelegate,
 
   WindowManagerDisplayRootMap window_manager_display_root_map_;
 
+  std::unique_ptr<WindowManagerDisplayRoot> external_mode_root_;
+
   DISALLOW_COPY_AND_ASSIGN(Display);
 };