Scale client area, hit test mask and bounds by device_scale_factor.

services/ui/public/cpp/tests/window_server_test_base.h

Index: services/ui/public/cpp/tests/window_server_test_base.h
diff --git a/services/ui/public/cpp/tests/window_server_test_base.h b/services/ui/public/cpp/tests/window_server_test_base.h
index 677ccc59bc882333e45685bfb418c98e6aa4a63b..6cbe7b7aa1cb6b6c8bed9bd8adc2e5d7ecfdcbf1 100644
--- a/services/ui/public/cpp/tests/window_server_test_base.h
+++ b/services/ui/public/cpp/tests/window_server_test_base.h
@@ -14,6 +14,7 @@
 #include "services/ui/public/cpp/window_manager_delegate.h"
 #include "services/ui/public/cpp/window_tree_client_delegate.h"
 #include "services/ui/public/interfaces/window_tree.mojom.h"
+#include "ui/display/test/test_screen.h"
 
 namespace ui {
 
@@ -110,6 +111,9 @@ class WindowServerTestBase
 
   WindowManagerClient* window_manager_client_;
 
+  // Dummy screen required to be the screen instance.
+  display::test::TestScreen test_screen_;
+
   bool window_tree_client_lost_connection_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WindowServerTestBase);