Add PlatformScreenDelegate and start implementation.

services/ui/ws/window_tree_host_factory.cc

Index: services/ui/ws/window_tree_host_factory.cc
diff --git a/services/ui/ws/window_tree_host_factory.cc b/services/ui/ws/window_tree_host_factory.cc
index 6bc66bf9b2b017e20196ce0640c93e4c6d04cc8c..e24fd082344eb3b1ecd64436b10b8edd3c3c86e0 100644
--- a/services/ui/ws/window_tree_host_factory.cc
+++ b/services/ui/ws/window_tree_host_factory.cc
@@ -12,13 +12,12 @@
 namespace ui {
 namespace ws {
 
-WindowTreeHostFactory::WindowTreeHostFactory(
-    WindowServer* window_server,
-    const UserId& user_id,
-    const PlatformDisplayInitParams& platform_display_init_params)
-    : window_server_(window_server),
-      user_id_(user_id),
-      platform_display_init_params_(platform_display_init_params) {}
+WindowTreeHostFactory::WindowTreeHostFactory(WindowServer* window_server,
+                                             const UserId& user_id)
+    : window_server_(window_server), user_id_(user_id) {
+  platform_display_init_params_.surfaces_state =
+      window_server_->GetSurfacesState();
+}
 
 WindowTreeHostFactory::~WindowTreeHostFactory() {}