GN: Tighten up test target visibility + refactorings

webrtc/modules/pacing/BUILD.gn

Index: webrtc/modules/pacing/BUILD.gn
diff --git a/webrtc/modules/pacing/BUILD.gn b/webrtc/modules/pacing/BUILD.gn
index d1cf656e6d1ce42c1e02d8b1091616ba4e0491d0..ce2356e28a1bf181a303da0f3b5ad6734176332c 100644
--- a/webrtc/modules/pacing/BUILD.gn
+++ b/webrtc/modules/pacing/BUILD.gn
@@ -39,6 +39,13 @@ rtc_static_library("pacing") {
 if (rtc_include_tests) {
   rtc_source_set("pacing_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 = [
       "alr_detector_unittest.cc",
       "bitrate_prober_unittest.cc",
@@ -52,7 +59,7 @@ if (rtc_include_tests) {
       "../../system_wrappers:system_wrappers",
       "../../test:test_support",
       "../rtp_rtcp",
-      "../rtp_rtcp:rtp_rtcp_unittests",
+      "../rtp_rtcp:mock_rtp_rtcp",
       "//testing/gmock",
     ]