Add service name constant for UI service.

ash/mus/accelerators/accelerator_controller_delegate_mus.cc

Index: ash/mus/accelerators/accelerator_controller_delegate_mus.cc
diff --git a/ash/mus/accelerators/accelerator_controller_delegate_mus.cc b/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
index cb95a7c92675ad0d19c3c5f32bf8ee27eb4d6504..f1664b5869f03f0ee977717b3e9518d5784684f5 100644
--- a/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
+++ b/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "mash/public/interfaces/launchable.mojom.h"
 #include "services/service_manager/public/cpp/connector.h"
+#include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/display/display_controller.mojom.h"
 #include "services/ui/public/interfaces/display/test_display_controller.mojom.h"
 
@@ -102,7 +103,7 @@ void AcceleratorControllerDelegateMus::PerformAction(
     case DEV_ADD_REMOVE_DISPLAY: {
       display::mojom::TestDisplayControllerPtr test_display_controller;
       window_manager_->connector()->ConnectToInterface(
-          "ui", &test_display_controller);
+          ui::mojom::kServiceName, &test_display_controller);
       test_display_controller->ToggleAddRemoveDisplay();
       break;
     }
@@ -111,7 +112,7 @@ void AcceleratorControllerDelegateMus::PerformAction(
       // key to toggle display size in mus. This should be removed by launch.
       display::mojom::TestDisplayControllerPtr test_display_controller;
       window_manager_->connector()->ConnectToInterface(
-          "ui", &test_display_controller);
+          ui::mojom::kServiceName, &test_display_controller);
       test_display_controller->ToggleDisplayResolution();
       break;
     }