Move the test template to //testing/test.gni (part 2)

mojo/services/html_viewer/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("//mojo/public/mojo.gni")
 import("//mojo/public/mojo_application.gni")
+import("//testing/rules.gni")
 
 source_set("lib") {
   sources = [
     "ax_provider_impl.cc",
     "ax_provider_impl.h",
     "blink_basic_type_converters.cc",
     "blink_basic_type_converters.h",
     "blink_input_events_type_converters.cc",
     "blink_input_events_type_converters.h",
     "blink_platform_impl.cc",
@@ skipping 79 matching lines @@
 test("tests") {
   output_name = "html_viewer_unittests"
   sources = [
     "ax_provider_impl_unittest.cc",
   ]
   deps = [
     ":lib",
     "//base/test:run_all_unittests",
   ]
 }