mus: Changes SetDisplayRoot() to create actual display

services/ui/ws/test_utils.cc

Index: services/ui/ws/test_utils.cc
diff --git a/services/ui/ws/test_utils.cc b/services/ui/ws/test_utils.cc
index 50cbcd2791604c94c27aebfd915f2867dfec0dff..378cf9324ca1fc26b9997bedd51c5db9e3358097 100644
--- a/services/ui/ws/test_utils.cc
+++ b/services/ui/ws/test_utils.cc
@@ -16,6 +16,7 @@
 #include "services/ui/ws/window_manager_access_policy.h"
 #include "services/ui/ws/window_manager_window_tree_factory.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "ui/display/screen_base.h"
 #include "ui/gfx/geometry/dip_util.h"
 
 namespace ui {
@@ -523,6 +524,12 @@ bool TestWindowServerDelegate::IsTestConfig() const {
   return true;
 }
 
+display::ScreenBase* TestWindowServerDelegate::GetScreen() {
+  if (!screen_)
+    screen_ = base::MakeUnique<display::ScreenBase>();
+  return screen_.get();
+}
+
 // WindowServerTestHelper  ---------------------------------------------------
 
 WindowServerTestHelper::WindowServerTestHelper()