GN: Tighten up test target visibility + refactorings

webrtc/tools/network_tester/BUILD.gn

 # Copyright (c) 2017 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")
 import("//third_party/protobuf/proto_library.gni")
@@ skipping 47 matching lines @@
     bundle_data("network_tester_unittests_bundle_data") {
       testonly = true
       sources = network_tester_unittests_resources
       outputs = [
         "{{bundle_resources_dir}}/{{source_file_part}}",
       ]
     }
   }
 
   rtc_source_set("network_tester_unittests") {
+    testonly = true
+    if (!is_android && !is_ios) {  # Generated targets makes this check break.
+      visibility = [ "//webrtc/tools:tools_unittests" ]
+    }
     sources = [
       "network_tester_unittest.cc",
     ]
 
-    testonly = true
     deps = [
       ":network_tester",
       "//testing/gtest",
       "//webrtc/base:rtc_base_tests_utils",
       "//webrtc/test:test_support",
     ]
 
     if (is_ios) {
       deps += [ ":network_tester_unittests_bundle_data" ]
     }
 
     defines = [
       "GTEST_RELATIVE_PATH",
       "WEBRTC_NETWORK_TESTER_TEST_ENABLED",
     ]
 
     data = network_tester_unittests_resources
 
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
   }
 }