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diff --git a/third_party/libwebrtc/rtc_base/synchronization/sequence_checker_internal.h b/third_party/libwebrtc/rtc_base/synchronization/sequence_checker_internal.h
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+++ b/third_party/libwebrtc/rtc_base/synchronization/sequence_checker_internal.h
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+/*
+ *  Copyright 2020 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.
+ */
+#ifndef RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_INTERNAL_H_
+#define RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_INTERNAL_H_
+
+#include <string>
+#include <type_traits>
+
+#include "api/task_queue/task_queue_base.h"
+#include "rtc_base/platform_thread_types.h"
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace webrtc {
+namespace webrtc_sequence_checker_internal {
+
+// Real implementation of SequenceChecker, for use in debug mode, or
+// for temporary use in release mode (e.g. to RTC_CHECK on a threading issue
+// seen only in the wild).
+//
+// Note: You should almost always use the SequenceChecker class to get the
+// right version for your build configuration.
+class RTC_EXPORT SequenceCheckerImpl {
+ public:
+  explicit SequenceCheckerImpl(bool attach_to_current_thread);
+  explicit SequenceCheckerImpl(TaskQueueBase* attached_queue);
+  ~SequenceCheckerImpl() = default;
+
+  bool IsCurrent() const;
+  // Changes the task queue or thread that is checked for in IsCurrent. This can
+  // be useful when an object may be created on one task queue / thread and then
+  // used exclusively on another thread.
+  void Detach();
+
+  // Returns a string that is formatted to match with the error string printed
+  // by RTC_CHECK() when a condition is not met.
+  // This is used in conjunction with the RTC_DCHECK_RUN_ON() macro.
+  std::string ExpectationToString() const;
+
+ private:
+  mutable Mutex lock_;
+  // These are mutable so that IsCurrent can set them.
+  mutable bool attached_ RTC_GUARDED_BY(lock_);
+  mutable rtc::PlatformThreadRef valid_thread_ RTC_GUARDED_BY(lock_);
+  mutable const TaskQueueBase* valid_queue_ RTC_GUARDED_BY(lock_);
+};
+
+// Do nothing implementation, for use in release mode.
+//
+// Note: You should almost always use the SequenceChecker class to get the
+// right version for your build configuration.
+class SequenceCheckerDoNothing {
+ public:
+  explicit SequenceCheckerDoNothing(bool attach_to_current_thread) {}
+  explicit SequenceCheckerDoNothing(TaskQueueBase* attached_queue) {}
+  bool IsCurrent() const { return true; }
+  void Detach() {}
+};
+
+template <typename ThreadLikeObject>
+std::enable_if_t<std::is_base_of_v<SequenceCheckerImpl, ThreadLikeObject>,
+                 std::string>
+ExpectationToString(const ThreadLikeObject* checker) {
+#if RTC_DCHECK_IS_ON
+  return checker->ExpectationToString();
+#else
+  return std::string();
+#endif
+}
+
+// Catch-all implementation for types other than explicitly supported above.
+template <typename ThreadLikeObject>
+std::enable_if_t<!std::is_base_of_v<SequenceCheckerImpl, ThreadLikeObject>,
+                 std::string>
+ExpectationToString(const ThreadLikeObject*) {
+  return std::string();
+}
+
+}  // namespace webrtc_sequence_checker_internal
+}  // namespace webrtc
+
+#endif  // RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_INTERNAL_H_