GN: Tighten up test target visibility + refactorings

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("../../webrtc.gni")
 
@@ skipping 24 matching lines @@
     "../../base:rtc_task_queue",
     "../../common_audio",
     "../../system_wrappers",
     "../media_file",
   ]
 }
 
 if (rtc_include_tests) {
   rtc_source_set("utility_unittests") {
     testonly = true
+
+    # Skip restricting visibility on mobile platforms since the tests on those
+    # gets additional generated targets which would require many lines here to
+    # cover (which would be confusing to read and hard to maintain).
+    if (!is_android && !is_ios) {
+      visibility = [ "//webrtc/modules:modules_unittests" ]
+    }
     sources = [
       "source/process_thread_impl_unittest.cc",
     ]
     deps = [
       ":utility",
       "../../base:rtc_task_queue",
       "../../test:test_support",
       "//testing/gmock",
     ]
   }
 }