gpu: Make the mus-gpu client-lib test-friendly.

services/ui/public/cpp/tests/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 source_set("tests") {
   testonly = true
 
   sources = [
+    "gpu_unittest.cc",
     "property_type_converters_unittest.cc",
   ]
 
   deps = [
     "//base",
     "//base/test:test_support",
     "//mojo/common:common_base",
     "//mojo/edk/system",
     "//mojo/public/cpp/system",
     "//services/service_manager/public/cpp",
     "//services/ui/public/cpp",
     "//testing/gtest",
     "//ui/gfx:test_support",
     "//ui/gfx/geometry",
     "//ui/gfx/geometry/mojo",
   ]
 
   if (use_x11) {
     deps += [ "//ui/gfx/x" ]
   }
 }