GN: Tighten up test target visibility + refactorings

webrtc/modules/utility/BUILD.gn

Index: webrtc/modules/utility/BUILD.gn
diff --git a/webrtc/modules/utility/BUILD.gn b/webrtc/modules/utility/BUILD.gn
index ae042d4c2237ac02038293304c3f645008eb2523..3d32ac27d57eeaec3d83c7cb0bdeb7065289c5c3 100644
--- a/webrtc/modules/utility/BUILD.gn
+++ b/webrtc/modules/utility/BUILD.gn
@@ -42,6 +42,13 @@ rtc_static_library("utility") {
 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",
     ]