Update from https://crrev.com/312398

mojo/dart/embedder/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/public/tools/bindings/mojom.gni")
+import("//testing/test.gni")
 
 action("generate_test_snapshot_bin") {
   deps = [
     "//dart/runtime/bin:gen_snapshot",
   ]
   inputs = [
     "test_snapshot.dart",
     "//dart/runtime/tools/create_snapshot_bin.py",
     "//mojo/dart/embedder/builtin.dart",
     "//mojo/public/dart/bindings.dart",
@@ skipping 116 matching lines @@
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//testing/gtest",
   ]
 }
 
 mojom("dart_to_cpp_bindings") {
   sources = [
     "dart_to_cpp.mojom",
   ]
 }