Add service name constant for UI service.

ash/mus/app_launch_unittest.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 "base/bind.h"
 #include "base/command_line.h"
 #include "base/run_loop.h"
 #include "services/service_manager/public/cpp/service_test.h"
+#include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/window_server_test.mojom.h"
 
 namespace ash {
 namespace mus {
 
 void RunCallback(bool* success, const base::Closure& callback, bool result) {
   *success = result;
   callback.Run();
 }
 
@@ skipping 18 matching lines @@
 #if defined(USE_OZONE)
 #define MAYBE_TestQuickLaunch TestQuickLaunch
 #else
 #define MAYBE_TestQuickLaunch DISABLED_TestQuickLaunch
 #endif  // defined(USE_OZONE)
 TEST_F(AppLaunchTest, MAYBE_TestQuickLaunch) {
   connector()->Connect("ash");
   connector()->Connect("quick_launch");
 
   ui::mojom::WindowServerTestPtr test_interface;
-  connector()->ConnectToInterface("ui", &test_interface);
+  connector()->ConnectToInterface(ui::mojom::kServiceName, &test_interface);
 
   base::RunLoop run_loop;
   bool success = false;
   test_interface->EnsureClientHasDrawnWindow(
       "quick_launch",
       base::Bind(&RunCallback, &success, run_loop.QuitClosure()));
   run_loop.Run();
   EXPECT_TRUE(success);
 }
 
 }  // namespace mus
 }  // namespace ash