Add FakeDisplayDelegate for off device usage.

services/ui/display/platform_screen_ozone.h

Index: services/ui/display/platform_screen_ozone.h
diff --git a/services/ui/display/platform_screen_ozone.h b/services/ui/display/platform_screen_ozone.h
index 521ead33aa394f005efe4fc06a817f032b788894..8e2361f89e228a368be52e2b2fddf1b95d0c6865 100644
--- a/services/ui/display/platform_screen_ozone.h
+++ b/services/ui/display/platform_screen_ozone.h
@@ -19,6 +19,7 @@
 #include "services/ui/public/interfaces/display/display_controller.mojom.h"
 #include "ui/display/chromeos/display_configurator.h"
 #include "ui/display/display.h"
+#include "ui/display/types/fake_display_controller.h"
 
 namespace display {
 
@@ -102,6 +103,14 @@ class PlatformScreenOzone
   ui::DisplayConfigurator display_configurator_;
   PlatformScreenDelegate* delegate_ = nullptr;
 
+  // If not null it provides a way to modify the display state when running off
+  // device (eg. running mustash on Linux).
+  FakeDisplayController* fake_display_controller_ = nullptr;
+
+  // Tracks if we've made a display configuration change and want to wait for
+  // the display configuration to update before making further changes.
+  bool wait_for_display_config_update_ = false;
+
   // TODO(kylechar): These values can/should be replaced by DisplayLayout.
   int64_t primary_display_id_ = display::Display::kInvalidDisplayID;
   std::vector<DisplayInfo> cached_displays_;