GN: Tighten up test target visibility + refactorings

webrtc/modules/congestion_controller/BUILD.gn

Index: webrtc/modules/congestion_controller/BUILD.gn
diff --git a/webrtc/modules/congestion_controller/BUILD.gn b/webrtc/modules/congestion_controller/BUILD.gn
index a7a67e20f3cab8124101ef278b5a06c3796a290b..84bd356cf472b51b5e7b607c16dbbaf4b9c7d140 100644
--- a/webrtc/modules/congestion_controller/BUILD.gn
+++ b/webrtc/modules/congestion_controller/BUILD.gn
@@ -64,6 +64,9 @@ rtc_static_library("congestion_controller") {
 if (rtc_include_tests) {
   rtc_source_set("congestion_controller_unittests") {
     testonly = true
+    if (!is_android && !is_ios) {  # Generated targets makes this check break.
+      visibility = [ "//webrtc/modules:modules_unittests" ]
+    }
     sources = [
       "congestion_controller_unittest.cc",
       "congestion_controller_unittests_helper.cc",
@@ -86,8 +89,8 @@ if (rtc_include_tests) {
       "../../test:test_support",
       "../bitrate_controller:bitrate_controller",
       "../pacing:pacing",
+      "../remote_bitrate_estimator:mock_remote_bitrate_observer",
       "../remote_bitrate_estimator:remote_bitrate_estimator",
-      "../remote_bitrate_estimator:remote_bitrate_estimator_unittests",
       "../rtp_rtcp:rtp_rtcp",
       "//testing/gmock",
     ]