Add FakeDisplayDelegate for off device usage.

ui/display/chromeos/x11/native_display_delegate_x11.cc

Index: ui/display/chromeos/x11/native_display_delegate_x11.cc
diff --git a/ui/display/chromeos/x11/native_display_delegate_x11.cc b/ui/display/chromeos/x11/native_display_delegate_x11.cc
index 7e4db1524102fdafd3222526c626ce4fe0583eaf..920851edc68a364978063e31dff6e30614bd7ead 100644
--- a/ui/display/chromeos/x11/native_display_delegate_x11.cc
+++ b/ui/display/chromeos/x11/native_display_delegate_x11.cc
@@ -282,6 +282,11 @@ void NativeDisplayDelegateX11::RemoveObserver(NativeDisplayObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+display::FakeDisplayController*
+NativeDisplayDelegateX11::GetFakeDisplayController() {
+  return nullptr;
+}
+
 void NativeDisplayDelegateX11::InitModes() {
   CHECK(screen_) << "Server not grabbed";