GN: Use rtc_include_tests variable to exclude tests.

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 614 matching lines @@
     sources -= [ "ifaddrs_converter.cc" ]
   }
 }
 
 source_set("gtest_prod") {
   sources = [
     "gtest_prod_util.h",
   ]
 }
 
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   config("rtc_base_test_utils_exported_config") {
     defines = [ "GTEST_RELATIVE_PATH" ]
   }
 
   source_set("rtc_base_test_utils") {
     testonly = true
     sources = [
       # Also use this as a convenient dumping ground for misc files that are
       # included by multiple targets below.
       "fakenetwork.h",
@@ skipping 12 matching lines @@
     ]
     deps = [
       ":rtc_base",
       "../test:field_trial",
     ]
     public_deps = [
       "//testing/gtest",
     ]
   }
 }