Revert of Support base::test::ScopedTaskEnvironment and content::TestBrowserThreadBundle in the same scope.

content/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("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
@@ skipping 1344 matching lines @@
     "../common/sandbox_mac_diraccess_unittest.mm",
     "../common/sandbox_mac_fontloading_unittest.mm",
     "../common/sandbox_mac_system_access_unittest.mm",
     "../common/sandbox_mac_unittest_helper.h",
     "../common/sandbox_mac_unittest_helper.mm",
     "../common/service_manager/service_manager_connection_impl_unittest.cc",
     "../common/service_worker/service_worker_utils_unittest.cc",
     "../common/webplugininfo_unittest.cc",
     "../network/url_loader_unittest.cc",
     "../public/test/referrer_unittest.cc",
-    "../public/test/test_browser_thread_bundle_unittest.cc",
     "../renderer/android/disambiguation_popup_helper_unittest.cc",
     "../renderer/bmp_image_decoder_unittest.cc",
     "../renderer/categorized_worker_pool_unittest.cc",
     "../renderer/device_sensors/device_motion_event_pump_unittest.cc",
     "../renderer/device_sensors/device_orientation_event_pump_unittest.cc",
     "../renderer/dom_storage/dom_storage_cached_area_unittest.cc",
     "../renderer/gpu/compositor_forwarding_message_filter_unittest.cc",
     "../renderer/gpu/frame_swap_message_queue_unittest.cc",
     "../renderer/gpu/queue_message_swap_promise_unittest.cc",
     "../renderer/gpu/render_widget_compositor_unittest.cc",
@@ skipping 452 matching lines @@
   if (is_android) {
     deps += [ "//testing/android/native_test:native_test_native_code" ]
   }
 }
 
 group("fuzzers") {
   deps = [
     "//content/test/fuzzer",
   ]
 }