Refactor webrtc/modules/rtp_rtcp for GN check

webrtc/modules/BUILD.gn

 # Copyright (c) 2016 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("../build/webrtc.gni")
 import("audio_coding/audio_coding.gni")
@@ skipping 403 matching lines @@
       "remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time_unittest.cc",
       "remote_bitrate_estimator/remote_bitrate_estimator_single_stream_unittest.cc",
       "remote_bitrate_estimator/remote_bitrate_estimator_unittest_helper.cc",
       "remote_bitrate_estimator/remote_bitrate_estimator_unittest_helper.h",
       "remote_bitrate_estimator/remote_estimator_proxy_unittest.cc",
       "remote_bitrate_estimator/send_time_history_unittest.cc",
       "remote_bitrate_estimator/test/bwe_test_framework_unittest.cc",
       "remote_bitrate_estimator/test/bwe_unittest.cc",
       "remote_bitrate_estimator/test/estimators/nada_unittest.cc",
       "remote_bitrate_estimator/test/metric_recorder_unittest.cc",
+      "rtp_rtcp/mocks/mock_rtp_rtcp.h",
       "rtp_rtcp/source/byte_io_unittest.cc",
       "rtp_rtcp/source/fec_test_helper.cc",
       "rtp_rtcp/source/fec_test_helper.h",
       "rtp_rtcp/source/flexfec_header_reader_writer_unittest.cc",
       "rtp_rtcp/source/flexfec_receiver_unittest.cc",
       "rtp_rtcp/source/flexfec_sender_unittest.cc",
       "rtp_rtcp/source/nack_rtx_unittest.cc",
       "rtp_rtcp/source/packet_loss_stats_unittest.cc",
       "rtp_rtcp/source/playout_delay_oracle_unittest.cc",
       "rtp_rtcp/source/receive_statistics_unittest.cc",
@@ skipping 318 matching lines @@
       "../test:test_common",
       "../test:test_main",
       "remote_bitrate_estimator:bwe_simulator_lib",
       "video_capture",
       "//testing/gmock",
       "//testing/gtest",
       "//third_party/gflags",
     ]
   }
 }