Remove rtcp_utility as mostly unused.

webrtc/modules/rtp_rtcp/source/rtcp_nack_stats.cc

+/*
+ *  Copyright (c) 2017 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.
+ */
+
+#include "webrtc/modules/rtp_rtcp/source/rtcp_nack_stats.h"
+
+#include "webrtc/modules/include/module_common_types.h"
+
+namespace webrtc {
+
+RtcpNackStats::RtcpNackStats()
+    : max_sequence_number_(0),
+      requests_(0),
+      unique_requests_(0) {}
+
+void RtcpNackStats::ReportRequest(uint16_t sequence_number) {
+  if (requests_ == 0 ||
+      IsNewerSequenceNumber(sequence_number, max_sequence_number_)) {
+    max_sequence_number_ =  sequence_number;
+    ++unique_requests_;
+  }
+  ++requests_;
+}
+
+}  // namespace webrtc