GN: Refactor modules_unittests to eliminate package boundary violations.

webrtc/modules/utility/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/webrtc.gni")
 
@@ skipping 24 matching lines @@
     "../../base:rtc_task_queue",
     "../../common_audio",
     "../../system_wrappers",
     "../audio_coding",
     "../audio_coding:audio_format_conversion",
     "../audio_coding:builtin_audio_decoder_factory",
     "../audio_coding:rent_a_codec",
     "../media_file",
   ]
 }
+
+if (rtc_include_tests) {
+  rtc_source_set("utility_unittests") {
+    testonly = true
+    sources = [
+      "source/process_thread_impl_unittest.cc",
+    ]
+    deps = [
+      ":utility",
+      "../../base:rtc_task_queue",
+      "../../test:test_support",
+      "//testing/gmock",
+    ]
+  }
+}