Rename FecReceiver to UlpfecReceiver.

BUG=webrtc:5654

Review-Url: https://codereview.webrtc.org/2451643002
Cr-Commit-Position: refs/heads/master@{#14846}
diff --git a/webrtc/modules/BUILD.gn b/webrtc/modules/BUILD.gn
index b444e80..c5330ea 100644
--- a/webrtc/modules/BUILD.gn
+++ b/webrtc/modules/BUILD.gn
@@ -413,7 +413,6 @@
       "remote_bitrate_estimator/test/estimators/nada_unittest.cc",
       "remote_bitrate_estimator/test/metric_recorder_unittest.cc",
       "rtp_rtcp/source/byte_io_unittest.cc",
-      "rtp_rtcp/source/fec_receiver_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",
@@ -466,6 +465,7 @@
       "rtp_rtcp/source/rtp_sender_unittest.cc",
       "rtp_rtcp/source/time_util_unittest.cc",
       "rtp_rtcp/source/ulpfec_header_reader_writer_unittest.cc",
+      "rtp_rtcp/source/ulpfec_receiver_unittest.cc",
       "rtp_rtcp/source/vp8_partition_aggregator_unittest.cc",
       "rtp_rtcp/test/testAPI/test_api.cc",
       "rtp_rtcp/test/testAPI/test_api.h",