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 f4b244d4f7fbc2987bd788457376e95a80926c9e..b0e170386efd798b1fbdb37f1667be738e0bc8ec 100644
--- a/services/ui/ws/display.h
+++ b/services/ui/ws/display.h
@@ -162,7 +162,11 @@ 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
@@ -219,6 +223,8 @@ class Display : public PlatformDisplayDelegate,
 
   WindowManagerDisplayRootMap window_manager_display_root_map_;
 
+  std::unique_ptr<WindowManagerDisplayRoot> external_mode_root_;
+
   DISALLOW_COPY_AND_ASSIGN(Display);
 };