Update to current webrtc library

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

webrtc/rtc_base/race_checker.cc

@@ -0,0 +1,54 @@
+/*
+ *  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.
+ */
+
+#include "rtc_base/race_checker.h"
+
+namespace rtc {
+
+RaceChecker::RaceChecker() {}
+
+// Note that the implementation here is in itself racy, but we pretend it does
+// not matter because we want this useful in release builds without having to
+// pay the cost of using atomics. A race hitting the race checker is likely to
+// cause access_count_ to diverge from zero and therefore cause the ThreadRef
+// comparison to fail, signaling a race, although it may not be in the exact
+// spot where a race *first* appeared in the code we're trying to protect. There
+// is also a chance that an actual race is missed, however the probability of
+// that has been considered small enough to be an acceptable trade off.
+bool RaceChecker::Acquire() const {
+  const PlatformThreadRef current_thread = CurrentThreadRef();
+  // Set new accessing thread if this is a new use.
+  if (access_count_++ == 0)
+    accessing_thread_ = current_thread;
+  // If this is being used concurrently this check will fail for the second
+  // thread entering since it won't set the thread. Recursive use of checked
+  // methods are OK since the accessing thread remains the same.
+  const PlatformThreadRef accessing_thread = accessing_thread_;
+  return IsThreadRefEqual(accessing_thread, current_thread);
+}
+
+void RaceChecker::Release() const {
+  --access_count_;
+}
+
+namespace internal {
+RaceCheckerScope::RaceCheckerScope(const RaceChecker* race_checker)
+    : race_checker_(race_checker), race_check_ok_(race_checker->Acquire()) {}
+
+bool RaceCheckerScope::RaceDetected() const {
+  return !race_check_ok_;
+}
+
+RaceCheckerScope::~RaceCheckerScope() {
+  race_checker_->Release();
+}
+
+}  // namespace internal
+}  // namespace rtc