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

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

Index: services/ui/public/cpp/tests/window_server_test_base.cc
diff --git a/services/ui/public/cpp/tests/window_server_test_base.cc b/services/ui/public/cpp/tests/window_server_test_base.cc
index 80835810c0514776cb045ecc1732f10bc0b19ad9..55f5e9d2120664a68185aa25187b56ed101d2bfa 100644
--- a/services/ui/public/cpp/tests/window_server_test_base.cc
+++ b/services/ui/public/cpp/tests/window_server_test_base.cc
@@ -35,6 +35,7 @@ WindowServerTestBase::WindowServerTestBase()
       window_manager_client_(nullptr) {}
 
 WindowServerTestBase::~WindowServerTestBase() {
+  display::Screen::SetScreenInstance(nullptr);
   window_tree_clients_.clear();
 }
 
@@ -80,6 +81,7 @@ void WindowServerTestBase::DeleteWindowTreeClient(
 void WindowServerTestBase::SetUp() {
   WindowServerServiceTestBase::SetUp();
 
+  display::Screen::SetScreenInstance(&test_screen_);
   std::unique_ptr<WindowTreeClient> window_manager_window_tree_client =
       base::MakeUnique<WindowTreeClient>(this, this);
   window_manager_window_tree_client->ConnectAsWindowManager(connector());