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

gin/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/module_args/v8.gni")
+import("//testing/test.gni")
 
 component("gin") {
   sources = [
     "arguments.cc",
     "arguments.h",
     "array_buffer.cc",
     "array_buffer.h",
     "context_holder.cc",
     "converter.cc",
     "converter.h",
@@ skipping 140 matching lines @@
     "test/run_js_tests.cc",
     "wrappable_unittest.cc",
   ]
 
   deps = [
     ":gin_test",
     "//base/test:test_support",
     "//v8",
   ]
 }