GN: Tighten up test target visibility + refactorings

webrtc/modules/congestion_controller/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 46 matching lines @@
     "../pacing",
     "../remote_bitrate_estimator",
     "../rtp_rtcp",
     "../utility",
   ]
 }
 
 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",
       "congestion_controller_unittests_helper.h",
       "delay_based_bwe_unittest.cc",
       "delay_based_bwe_unittest_helper.cc",
       "delay_based_bwe_unittest_helper.h",
       "median_slope_estimator_unittest.cc",
       "probe_bitrate_estimator_unittest.cc",
       "probe_controller_unittest.cc",
       "probing_interval_estimator_unittest.cc",
       "transport_feedback_adapter_unittest.cc",
       "trendline_estimator_unittest.cc",
     ]
     deps = [
       ":congestion_controller",
       "../../base:rtc_base_approved",
       "../../system_wrappers:system_wrappers",
       "../../test:field_trial",
       "../../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",
     ]
     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" ]
     }
   }
 }