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diff --git a/third_party/libwebrtc/rtc_base/buffer.h b/third_party/libwebrtc/rtc_base/buffer.h
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+++ b/third_party/libwebrtc/rtc_base/buffer.h
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+/*
+ *  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.
+ */
+
+#ifndef RTC_BASE_BUFFER_H_
+#define RTC_BASE_BUFFER_H_
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <cstring>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+#include "api/array_view.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/type_traits.h"
+#include "rtc_base/zero_memory.h"
+
+namespace rtc {
+
+namespace internal {
+
+// (Internal; please don't use outside this file.) Determines if elements of
+// type U are compatible with a BufferT<T>. For most types, we just ignore
+// top-level const and forbid top-level volatile and require T and U to be
+// otherwise equal, but all byte-sized integers (notably char, int8_t, and
+// uint8_t) are compatible with each other. (Note: We aim to get rid of this
+// behavior, and treat all types the same.)
+template <typename T, typename U>
+struct BufferCompat {
+  static constexpr bool value =
+      !std::is_volatile<U>::value &&
+      ((std::is_integral<T>::value && sizeof(T) == 1)
+           ? (std::is_integral<U>::value && sizeof(U) == 1)
+           : (std::is_same<T, typename std::remove_const<U>::type>::value));
+};
+
+}  // namespace internal
+
+// Basic buffer class, can be grown and shrunk dynamically.
+// Unlike std::string/vector, does not initialize data when increasing size.
+// If "ZeroOnFree" is true, any memory is explicitly cleared before releasing.
+// The type alias "ZeroOnFreeBuffer" below should be used instead of setting
+// "ZeroOnFree" in the template manually to "true".
+template <typename T, bool ZeroOnFree = false>
+class BufferT {
+  // We want T's destructor and default constructor to be trivial, i.e. perform
+  // no action, so that we don't have to touch the memory we allocate and
+  // deallocate. And we want T to be trivially copyable, so that we can copy T
+  // instances with std::memcpy. This is precisely the definition of a trivial
+  // type.
+  static_assert(std::is_trivial<T>::value, "T must be a trivial type.");
+
+  // This class relies heavily on being able to mutate its data.
+  static_assert(!std::is_const<T>::value, "T may not be const");
+
+ public:
+  using value_type = T;
+  using const_iterator = const T*;
+
+  // An empty BufferT.
+  BufferT() : size_(0), capacity_(0), data_(nullptr) {
+    RTC_DCHECK(IsConsistent());
+  }
+
+  // Disable copy construction and copy assignment, since copying a buffer is
+  // expensive enough that we want to force the user to be explicit about it.
+  BufferT(const BufferT&) = delete;
+  BufferT& operator=(const BufferT&) = delete;
+
+  BufferT(BufferT&& buf)
+      : size_(buf.size()),
+        capacity_(buf.capacity()),
+        data_(std::move(buf.data_)) {
+    RTC_DCHECK(IsConsistent());
+    buf.OnMovedFrom();
+  }
+
+  // Construct a buffer with the specified number of uninitialized elements.
+  explicit BufferT(size_t size) : BufferT(size, size) {}
+
+  BufferT(size_t size, size_t capacity)
+      : size_(size),
+        capacity_(std::max(size, capacity)),
+        data_(capacity_ > 0 ? new T[capacity_] : nullptr) {
+    RTC_DCHECK(IsConsistent());
+  }
+
+  // Construct a buffer and copy the specified number of elements into it.
+  template <typename U,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  BufferT(const U* data, size_t size) : BufferT(data, size, size) {}
+
+  template <typename U,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  BufferT(U* data, size_t size, size_t capacity) : BufferT(size, capacity) {
+    static_assert(sizeof(T) == sizeof(U), "");
+    if (size > 0) {
+      RTC_DCHECK(data);
+      std::memcpy(data_.get(), data, size * sizeof(U));
+    }
+  }
+
+  // Construct a buffer from the contents of an array.
+  template <typename U,
+            size_t N,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  BufferT(U (&array)[N]) : BufferT(array, N) {}
+
+  ~BufferT() { MaybeZeroCompleteBuffer(); }
+
+  // Implicit conversion to absl::string_view if T is compatible with char.
+  template <typename U = T>
+  operator typename std::enable_if<internal::BufferCompat<U, char>::value,
+                                   absl::string_view>::type() const {
+    return absl::string_view(data<char>(), size());
+  }
+
+  // Get a pointer to the data. Just .data() will give you a (const) T*, but if
+  // T is a byte-sized integer, you may also use .data<U>() for any other
+  // byte-sized integer U.
+  template <typename U = T,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  const U* data() const {
+    RTC_DCHECK(IsConsistent());
+    return reinterpret_cast<U*>(data_.get());
+  }
+
+  template <typename U = T,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  U* data() {
+    RTC_DCHECK(IsConsistent());
+    return reinterpret_cast<U*>(data_.get());
+  }
+
+  bool empty() const {
+    RTC_DCHECK(IsConsistent());
+    return size_ == 0;
+  }
+
+  size_t size() const {
+    RTC_DCHECK(IsConsistent());
+    return size_;
+  }
+
+  size_t capacity() const {
+    RTC_DCHECK(IsConsistent());
+    return capacity_;
+  }
+
+  BufferT& operator=(BufferT&& buf) {
+    RTC_DCHECK(buf.IsConsistent());
+    MaybeZeroCompleteBuffer();
+    size_ = buf.size_;
+    capacity_ = buf.capacity_;
+    using std::swap;
+    swap(data_, buf.data_);
+    buf.data_.reset();
+    buf.OnMovedFrom();
+    return *this;
+  }
+
+  bool operator==(const BufferT& buf) const {
+    RTC_DCHECK(IsConsistent());
+    if (size_ != buf.size_) {
+      return false;
+    }
+    if (std::is_integral<T>::value) {
+      // Optimization.
+      return std::memcmp(data_.get(), buf.data_.get(), size_ * sizeof(T)) == 0;
+    }
+    for (size_t i = 0; i < size_; ++i) {
+      if (data_[i] != buf.data_[i]) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  bool operator!=(const BufferT& buf) const { return !(*this == buf); }
+
+  T& operator[](size_t index) {
+    RTC_DCHECK_LT(index, size_);
+    return data()[index];
+  }
+
+  T operator[](size_t index) const {
+    RTC_DCHECK_LT(index, size_);
+    return data()[index];
+  }
+
+  T* begin() { return data(); }
+  T* end() { return data() + size(); }
+  const T* begin() const { return data(); }
+  const T* end() const { return data() + size(); }
+  const T* cbegin() const { return data(); }
+  const T* cend() const { return data() + size(); }
+
+  // The SetData functions replace the contents of the buffer. They accept the
+  // same input types as the constructors.
+  template <typename U,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  void SetData(const U* data, size_t size) {
+    RTC_DCHECK(IsConsistent());
+    const size_t old_size = size_;
+    size_ = 0;
+    AppendData(data, size);
+    if (ZeroOnFree && size_ < old_size) {
+      ZeroTrailingData(old_size - size_);
+    }
+  }
+
+  template <typename U,
+            size_t N,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  void SetData(const U (&array)[N]) {
+    SetData(array, N);
+  }
+
+  template <typename W,
+            typename std::enable_if<
+                HasDataAndSize<const W, const T>::value>::type* = nullptr>
+  void SetData(const W& w) {
+    SetData(w.data(), w.size());
+  }
+
+  // Replaces the data in the buffer with at most `max_elements` of data, using
+  // the function `setter`, which should have the following signature:
+  //
+  //   size_t setter(ArrayView<U> view)
+  //
+  // `setter` is given an appropriately typed ArrayView of length exactly
+  // `max_elements` that describes the area where it should write the data; it
+  // should return the number of elements actually written. (If it doesn't fill
+  // the whole ArrayView, it should leave the unused space at the end.)
+  template <typename U = T,
+            typename F,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  size_t SetData(size_t max_elements, F&& setter) {
+    RTC_DCHECK(IsConsistent());
+    const size_t old_size = size_;
+    size_ = 0;
+    const size_t written = AppendData<U>(max_elements, std::forward<F>(setter));
+    if (ZeroOnFree && size_ < old_size) {
+      ZeroTrailingData(old_size - size_);
+    }
+    return written;
+  }
+
+  // The AppendData functions add data to the end of the buffer. They accept
+  // the same input types as the constructors.
+  template <typename U,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  void AppendData(const U* data, size_t size) {
+    if (size == 0) {
+      return;
+    }
+    RTC_DCHECK(data);
+    RTC_DCHECK(IsConsistent());
+    const size_t new_size = size_ + size;
+    EnsureCapacityWithHeadroom(new_size, true);
+    static_assert(sizeof(T) == sizeof(U), "");
+    std::memcpy(data_.get() + size_, data, size * sizeof(U));
+    size_ = new_size;
+    RTC_DCHECK(IsConsistent());
+  }
+
+  template <typename U,
+            size_t N,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  void AppendData(const U (&array)[N]) {
+    AppendData(array, N);
+  }
+
+  template <typename W,
+            typename std::enable_if<
+                HasDataAndSize<const W, const T>::value>::type* = nullptr>
+  void AppendData(const W& w) {
+    AppendData(w.data(), w.size());
+  }
+
+  template <typename U,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  void AppendData(const U& item) {
+    AppendData(&item, 1);
+  }
+
+  // Appends at most `max_elements` to the end of the buffer, using the function
+  // `setter`, which should have the following signature:
+  //
+  //   size_t setter(ArrayView<U> view)
+  //
+  // `setter` is given an appropriately typed ArrayView of length exactly
+  // `max_elements` that describes the area where it should write the data; it
+  // should return the number of elements actually written. (If it doesn't fill
+  // the whole ArrayView, it should leave the unused space at the end.)
+  template <typename U = T,
+            typename F,
+            typename std::enable_if<
+                internal::BufferCompat<T, U>::value>::type* = nullptr>
+  size_t AppendData(size_t max_elements, F&& setter) {
+    RTC_DCHECK(IsConsistent());
+    const size_t old_size = size_;
+    SetSize(old_size + max_elements);
+    U* base_ptr = data<U>() + old_size;
+    size_t written_elements = setter(rtc::ArrayView<U>(base_ptr, max_elements));
+
+    RTC_CHECK_LE(written_elements, max_elements);
+    size_ = old_size + written_elements;
+    RTC_DCHECK(IsConsistent());
+    return written_elements;
+  }
+
+  // Sets the size of the buffer. If the new size is smaller than the old, the
+  // buffer contents will be kept but truncated; if the new size is greater,
+  // the existing contents will be kept and the new space will be
+  // uninitialized.
+  void SetSize(size_t size) {
+    const size_t old_size = size_;
+    EnsureCapacityWithHeadroom(size, true);
+    size_ = size;
+    if (ZeroOnFree && size_ < old_size) {
+      ZeroTrailingData(old_size - size_);
+    }
+  }
+
+  // Ensure that the buffer size can be increased to at least capacity without
+  // further reallocation. (Of course, this operation might need to reallocate
+  // the buffer.)
+  void EnsureCapacity(size_t capacity) {
+    // Don't allocate extra headroom, since the user is asking for a specific
+    // capacity.
+    EnsureCapacityWithHeadroom(capacity, false);
+  }
+
+  // Resets the buffer to zero size without altering capacity. Works even if the
+  // buffer has been moved from.
+  void Clear() {
+    MaybeZeroCompleteBuffer();
+    size_ = 0;
+    RTC_DCHECK(IsConsistent());
+  }
+
+  // Swaps two buffers. Also works for buffers that have been moved from.
+  friend void swap(BufferT& a, BufferT& b) {
+    using std::swap;
+    swap(a.size_, b.size_);
+    swap(a.capacity_, b.capacity_);
+    swap(a.data_, b.data_);
+  }
+
+ private:
+  void EnsureCapacityWithHeadroom(size_t capacity, bool extra_headroom) {
+    RTC_DCHECK(IsConsistent());
+    if (capacity <= capacity_)
+      return;
+
+    // If the caller asks for extra headroom, ensure that the new capacity is
+    // >= 1.5 times the old capacity. Any constant > 1 is sufficient to prevent
+    // quadratic behavior; as to why we pick 1.5 in particular, see
+    // https://github.com/facebook/folly/blob/master/folly/docs/FBVector.md and
+    // http://www.gahcep.com/cpp-internals-stl-vector-part-1/.
+    const size_t new_capacity =
+        extra_headroom ? std::max(capacity, capacity_ + capacity_ / 2)
+                       : capacity;
+
+    std::unique_ptr<T[]> new_data(new T[new_capacity]);
+    if (data_ != nullptr) {
+      std::memcpy(new_data.get(), data_.get(), size_ * sizeof(T));
+    }
+    MaybeZeroCompleteBuffer();
+    data_ = std::move(new_data);
+    capacity_ = new_capacity;
+    RTC_DCHECK(IsConsistent());
+  }
+
+  // Zero the complete buffer if template argument "ZeroOnFree" is true.
+  void MaybeZeroCompleteBuffer() {
+    if (ZeroOnFree && capacity_ > 0) {
+      // It would be sufficient to only zero "size_" elements, as all other
+      // methods already ensure that the unused capacity contains no sensitive
+      // data---but better safe than sorry.
+      ExplicitZeroMemory(data_.get(), capacity_ * sizeof(T));
+    }
+  }
+
+  // Zero the first "count" elements of unused capacity.
+  void ZeroTrailingData(size_t count) {
+    RTC_DCHECK(IsConsistent());
+    RTC_DCHECK_LE(count, capacity_ - size_);
+    ExplicitZeroMemory(data_.get() + size_, count * sizeof(T));
+  }
+
+  // Precondition for all methods except Clear, operator= and the destructor.
+  // Postcondition for all methods except move construction and move
+  // assignment, which leave the moved-from object in a possibly inconsistent
+  // state.
+  bool IsConsistent() const {
+    return (data_ || capacity_ == 0) && capacity_ >= size_;
+  }
+
+  // Called when *this has been moved from. Conceptually it's a no-op, but we
+  // can mutate the state slightly to help subsequent sanity checks catch bugs.
+  void OnMovedFrom() {
+    RTC_DCHECK(!data_);  // Our heap block should have been stolen.
+#if RTC_DCHECK_IS_ON
+    // Ensure that *this is always inconsistent, to provoke bugs.
+    size_ = 1;
+    capacity_ = 0;
+#else
+    // Make *this consistent and empty. Shouldn't be necessary, but better safe
+    // than sorry.
+    size_ = 0;
+    capacity_ = 0;
+#endif
+  }
+
+  size_t size_;
+  size_t capacity_;
+  std::unique_ptr<T[]> data_;
+};
+
+// By far the most common sort of buffer.
+using Buffer = BufferT<uint8_t>;
+
+// A buffer that zeros memory before releasing it.
+template <typename T>
+using ZeroOnFreeBuffer = BufferT<T, true>;
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_BUFFER_H_