Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/rtc_base/string_utils.cc

@@ -0,0 +1,53 @@
+/*
+ *  Copyright 2004 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 "rtc_base/string_utils.h"
+
+namespace rtc {
+
+size_t strcpyn(char* buffer,
+               size_t buflen,
+               const char* source,
+               size_t srclen /* = SIZE_UNKNOWN */) {
+  if (buflen <= 0)
+    return 0;
+
+  if (srclen == SIZE_UNKNOWN) {
+    srclen = strlen(source);
+  }
+  if (srclen >= buflen) {
+    srclen = buflen - 1;
+  }
+  memcpy(buffer, source, srclen);
+  buffer[srclen] = 0;
+  return srclen;
+}
+
+static const char kWhitespace[] = " \n\r\t";
+
+std::string string_trim(const std::string& s) {
+  std::string::size_type first = s.find_first_not_of(kWhitespace);
+  std::string::size_type last = s.find_last_not_of(kWhitespace);
+
+  if (first == std::string::npos || last == std::string::npos) {
+    return std::string("");
+  }
+
+  return s.substr(first, last - first + 1);
+}
+
+std::string ToHex(const int i) {
+  char buffer[50];
+  snprintf(buffer, sizeof(buffer), "%x", i);
+
+  return std::string(buffer);
+}
+
+}  // namespace rtc