Makes AshTestImpl::Create create the right impl based on config

components/exo/BUILD.gn

 # Copyright 2015 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/config/ui.gni")
 import("//testing/test.gni")
 
 source_set("exo") {
   sources = [
     "buffer.cc",
@@ skipping 75 matching lines @@
   sources = [
     "test/exo_test_base.cc",
     "test/exo_test_base.h",
     "test/exo_test_helper.cc",
     "test/exo_test_helper.h",
   ]
 
   deps = [
     ":exo",
     "//ash/public/cpp:ash_public_cpp",
-    "//ash/test:ash_with_aura_test_support",
     "//ash/test:test_support_without_content",
     "//base",
     "//gpu",
     "//skia",
     "//testing/gtest",
     "//ui/aura",
     "//ui/compositor",
     "//ui/gfx/geometry",
     "//ui/views",
     "//ui/wm:wm",
@@ skipping 50 matching lines @@
 test("exo_unittests") {
   sources = [
     "../../ash/test/ash_test_suite.cc",
     "../../ash/test/ash_test_suite.h",
     "test/run_all_unittests.cc",
   ]
 
   deps = [
     ":unit_tests",
     "//ash/public/cpp:ash_public_cpp",
-    "//ash/test:ash_with_aura_test_support",
     "//ash/test:test_support_without_content",
     "//base",
     "//base/test:test_support",
     "//device/gamepad:test_helpers",
     "//mojo/edk/embedder:headers",
     "//testing/gtest",
     "//ui/aura",
     "//ui/base",
     "//ui/compositor:test_support",
     "//ui/gl:test_support",
   ]
 
   data_deps = [
     "//ash/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 
   if (is_linux) {
     deps += [ "//components/exo/wayland:unit_tests" ]
   }
 }