Add service name constant for UI service.

services/ui/ime/test_ime_driver/test_ime_application.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/ime/test_ime_driver/test_ime_application.h"
 
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/service_manager/public/cpp/service_context.h"
 #include "services/ui/ime/test_ime_driver/test_ime_driver.h"
+#include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/ime.mojom.h"
 
 namespace ui {
 namespace test {
 
 TestIMEApplication::TestIMEApplication() {}
 
 TestIMEApplication::~TestIMEApplication() {}
 
 void TestIMEApplication::OnStart() {
   mojom::IMEDriverPtr ime_driver_ptr;
   mojo::MakeStrongBinding(base::MakeUnique<TestIMEDriver>(),
                           GetProxy(&ime_driver_ptr));
 
   ui::mojom::IMERegistrarPtr ime_registrar;
-  context()->connector()->ConnectToInterface("ui", &ime_registrar);
+  context()->connector()->ConnectToInterface(ui::mojom::kServiceName,
+                                             &ime_registrar);
   ime_registrar->RegisterDriver(std::move(ime_driver_ptr));
 }
 
 bool TestIMEApplication::OnConnect(
     const service_manager::ServiceInfo& remote_info,
     service_manager::InterfaceRegistry* registry) {
   return true;
 }
 
 }  // namespace test
 }  // namespace ui