Sync more GN unit tests with GYP.

components/keyed_service/core/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.
 
 component("core") {
   output_name = "keyed_service_core"
   sources = [
     "dependency_graph.cc",
     "dependency_graph.h",
     "dependency_manager.cc",
@@ skipping 17 matching lines @@
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   defines = [ "KEYED_SERVICE_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//base:prefs",
     "//components/user_prefs",
   ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "dependency_graph_unittest.cc",
+  ]
+  deps = [
+    ":core",
+    "//testing/gtest",
+  ]
+}