Sync more GN unit tests with GYP.

components/keyed_service/content/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.
 
 assert(!is_ios)
 
 component("content") {
   output_name = "keyed_service_content"
   sources = [
     "browser_context_dependency_manager.cc",
@@ skipping 13 matching lines @@
 
   defines = [ "KEYED_SERVICE_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
     "//components/keyed_service/core",
     "//content/public/common",
   ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "browser_context_dependency_manager_unittest.cc",
+  ]
+  deps = [
+    ":content",
+    "//testing/gtest",
+  ]
+}