Split the //mojo/public/cpp/test_support:test_utils target.

mojo/tests/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("//testing/test.gni")
 import("//mojo/public/mojo.gni")
 
 test("mojo_task_tracker_perftests") {
   deps = [
     "//base/test:test_support",
     "//mojo/edk/system",
     "//mojo/edk/test:test_support",
     "//mojo/edk/test:test_support_impl",
     "//mojo/environment:chromium",
     "//mojo/message_pump",
     "//mojo/public/c/test_support",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/bindings:callback",
     "//mojo/public/cpp/environment",
     "//mojo/public/cpp/system",
-    "//mojo/public/cpp/test_support:test_utils",
+    "//mojo/public/cpp/test_support",
     "//mojo/public/cpp/utility",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//base",
     "//testing/gtest",
   ]
 
   sources = [
     "../edk/test/run_all_perftests.cc",
     "task_tracker_perftest.cc",
   ]
 }