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

tools/gn/BUILD.gn

 # Copyright (c) 2013 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("//testing/test.gni")
+
 defines = [ "GN_BUILD" ]
 
 static_library("gn_lib") {
   sources = [
     "action_target_generator.cc",
     "action_target_generator.h",
     "action_values.cc",
     "action_values.h",
     "args.cc",
     "args.h",
@@ skipping 261 matching lines @@
 }
 
 executable("generate_test_gn_data") {
   sources = [
     "generate_test_gn_data.cc",
   ]
   deps = [
     "//base",
   ]
 }