Update from https://crrev.com/312398

mojo/edk/test/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_edk.gni")
+import("//testing/test.gni")
 
 mojo_edk_source_set("test_support") {
   testonly = true
   sources = [
     "multiprocess_test_helper.cc",
     "multiprocess_test_helper.h",
     "test_utils.h",
     "test_utils_posix.cc",
     "test_utils_win.cc",
   ]
@@ skipping 94 matching lines @@
     "../../public/cpp/system/tests",
   ]
 }
 
 test("mojo_public_utility_unittests") {
   deps = [
     ":run_all_unittests",
     "../../public/cpp/utility/tests",
   ]
 }