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diff --git a/third_party/libwebrtc/rtc_base/units/unit_base.h b/third_party/libwebrtc/rtc_base/units/unit_base.h
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+++ b/third_party/libwebrtc/rtc_base/units/unit_base.h
@@ -0,0 +1,326 @@
+/*
+ *  Copyright 2018 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_UNITS_UNIT_BASE_H_
+#define RTC_BASE_UNITS_UNIT_BASE_H_
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+#include <type_traits>
+
+#include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_conversions.h"
+
+namespace webrtc {
+namespace rtc_units_impl {
+
+// UnitBase is a base class for implementing custom value types with a specific
+// unit. It provides type safety and commonly useful operations. The underlying
+// storage is always an int64_t, it's up to the unit implementation to choose
+// what scale it represents.
+//
+// It's used like:
+// class MyUnit: public UnitBase<MyUnit> {...};
+//
+// Unit_T is the subclass representing the specific unit.
+template <class Unit_T>
+class UnitBase {
+ public:
+  UnitBase() = delete;
+  static constexpr Unit_T Zero() { return Unit_T(0); }
+  static constexpr Unit_T PlusInfinity() { return Unit_T(PlusInfinityVal()); }
+  static constexpr Unit_T MinusInfinity() { return Unit_T(MinusInfinityVal()); }
+
+  constexpr bool IsZero() const { return value_ == 0; }
+  constexpr bool IsFinite() const { return !IsInfinite(); }
+  constexpr bool IsInfinite() const {
+    return value_ == PlusInfinityVal() || value_ == MinusInfinityVal();
+  }
+  constexpr bool IsPlusInfinity() const { return value_ == PlusInfinityVal(); }
+  constexpr bool IsMinusInfinity() const {
+    return value_ == MinusInfinityVal();
+  }
+
+  constexpr bool operator==(const UnitBase<Unit_T>& other) const {
+    return value_ == other.value_;
+  }
+  constexpr bool operator!=(const UnitBase<Unit_T>& other) const {
+    return value_ != other.value_;
+  }
+  constexpr bool operator<=(const UnitBase<Unit_T>& other) const {
+    return value_ <= other.value_;
+  }
+  constexpr bool operator>=(const UnitBase<Unit_T>& other) const {
+    return value_ >= other.value_;
+  }
+  constexpr bool operator>(const UnitBase<Unit_T>& other) const {
+    return value_ > other.value_;
+  }
+  constexpr bool operator<(const UnitBase<Unit_T>& other) const {
+    return value_ < other.value_;
+  }
+  constexpr Unit_T RoundTo(const Unit_T& resolution) const {
+    RTC_DCHECK(IsFinite());
+    RTC_DCHECK(resolution.IsFinite());
+    RTC_DCHECK_GT(resolution.value_, 0);
+    return Unit_T((value_ + resolution.value_ / 2) / resolution.value_) *
+           resolution.value_;
+  }
+  constexpr Unit_T RoundUpTo(const Unit_T& resolution) const {
+    RTC_DCHECK(IsFinite());
+    RTC_DCHECK(resolution.IsFinite());
+    RTC_DCHECK_GT(resolution.value_, 0);
+    return Unit_T((value_ + resolution.value_ - 1) / resolution.value_) *
+           resolution.value_;
+  }
+  constexpr Unit_T RoundDownTo(const Unit_T& resolution) const {
+    RTC_DCHECK(IsFinite());
+    RTC_DCHECK(resolution.IsFinite());
+    RTC_DCHECK_GT(resolution.value_, 0);
+    return Unit_T(value_ / resolution.value_) * resolution.value_;
+  }
+
+ protected:
+  template <
+      typename T,
+      typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
+  static constexpr Unit_T FromValue(T value) {
+    if (Unit_T::one_sided)
+      RTC_DCHECK_GE(value, 0);
+    RTC_DCHECK_GT(value, MinusInfinityVal());
+    RTC_DCHECK_LT(value, PlusInfinityVal());
+    return Unit_T(rtc::dchecked_cast<int64_t>(value));
+  }
+  template <typename T,
+            typename std::enable_if<std::is_floating_point<T>::value>::type* =
+                nullptr>
+  static constexpr Unit_T FromValue(T value) {
+    if (value == std::numeric_limits<T>::infinity()) {
+      return PlusInfinity();
+    } else if (value == -std::numeric_limits<T>::infinity()) {
+      return MinusInfinity();
+    } else {
+      RTC_DCHECK(!std::isnan(value));
+      return FromValue(rtc::dchecked_cast<int64_t>(value));
+    }
+  }
+
+  template <
+      typename T,
+      typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
+  static constexpr Unit_T FromFraction(int64_t denominator, T value) {
+    if (Unit_T::one_sided)
+      RTC_DCHECK_GE(value, 0);
+    RTC_DCHECK_GT(value, MinusInfinityVal() / denominator);
+    RTC_DCHECK_LT(value, PlusInfinityVal() / denominator);
+    return Unit_T(rtc::dchecked_cast<int64_t>(value * denominator));
+  }
+  template <typename T,
+            typename std::enable_if<std::is_floating_point<T>::value>::type* =
+                nullptr>
+  static constexpr Unit_T FromFraction(int64_t denominator, T value) {
+    return FromValue(value * denominator);
+  }
+
+  template <typename T = int64_t>
+  constexpr typename std::enable_if<std::is_integral<T>::value, T>::type
+  ToValue() const {
+    RTC_DCHECK(IsFinite());
+    return rtc::dchecked_cast<T>(value_);
+  }
+  template <typename T>
+  constexpr typename std::enable_if<std::is_floating_point<T>::value, T>::type
+  ToValue() const {
+    return IsPlusInfinity()
+               ? std::numeric_limits<T>::infinity()
+               : IsMinusInfinity() ? -std::numeric_limits<T>::infinity()
+                                   : value_;
+  }
+  template <typename T>
+  constexpr T ToValueOr(T fallback_value) const {
+    return IsFinite() ? value_ : fallback_value;
+  }
+
+  template <int64_t Denominator, typename T = int64_t>
+  constexpr typename std::enable_if<std::is_integral<T>::value, T>::type
+  ToFraction() const {
+    RTC_DCHECK(IsFinite());
+    if (Unit_T::one_sided) {
+      return rtc::dchecked_cast<T>(
+          DivRoundPositiveToNearest(value_, Denominator));
+    } else {
+      return rtc::dchecked_cast<T>(DivRoundToNearest(value_, Denominator));
+    }
+  }
+  template <int64_t Denominator, typename T>
+  constexpr typename std::enable_if<std::is_floating_point<T>::value, T>::type
+  ToFraction() const {
+    return ToValue<T>() * (1 / static_cast<T>(Denominator));
+  }
+
+  template <int64_t Denominator>
+  constexpr int64_t ToFractionOr(int64_t fallback_value) const {
+    return IsFinite() ? Unit_T::one_sided
+                            ? DivRoundPositiveToNearest(value_, Denominator)
+                            : DivRoundToNearest(value_, Denominator)
+                      : fallback_value;
+  }
+
+  template <int64_t Factor, typename T = int64_t>
+  constexpr typename std::enable_if<std::is_integral<T>::value, T>::type
+  ToMultiple() const {
+    RTC_DCHECK_GE(ToValue(), std::numeric_limits<T>::min() / Factor);
+    RTC_DCHECK_LE(ToValue(), std::numeric_limits<T>::max() / Factor);
+    return rtc::dchecked_cast<T>(ToValue() * Factor);
+  }
+  template <int64_t Factor, typename T>
+  constexpr typename std::enable_if<std::is_floating_point<T>::value, T>::type
+  ToMultiple() const {
+    return ToValue<T>() * Factor;
+  }
+
+  explicit constexpr UnitBase(int64_t value) : value_(value) {}
+
+ private:
+  template <class RelativeUnit_T>
+  friend class RelativeUnit;
+
+  static inline constexpr int64_t PlusInfinityVal() {
+    return std::numeric_limits<int64_t>::max();
+  }
+  static inline constexpr int64_t MinusInfinityVal() {
+    return std::numeric_limits<int64_t>::min();
+  }
+
+  constexpr Unit_T& AsSubClassRef() { return static_cast<Unit_T&>(*this); }
+  constexpr const Unit_T& AsSubClassRef() const {
+    return static_cast<const Unit_T&>(*this);
+  }
+  // Assumes that n >= 0 and d > 0.
+  static constexpr int64_t DivRoundPositiveToNearest(int64_t n, int64_t d) {
+    return (n + d / 2) / d;
+  }
+  // Assumes that d > 0.
+  static constexpr int64_t DivRoundToNearest(int64_t n, int64_t d) {
+    return (n + (n >= 0 ? d / 2 : -d / 2)) / d;
+  }
+
+  int64_t value_;
+};
+
+// Extends UnitBase to provide operations for relative units, that is, units
+// that have a meaningful relation between values such that a += b is a
+// sensible thing to do. For a,b <- same unit.
+template <class Unit_T>
+class RelativeUnit : public UnitBase<Unit_T> {
+ public:
+  constexpr Unit_T Clamped(Unit_T min_value, Unit_T max_value) const {
+    return std::max(min_value,
+                    std::min(UnitBase<Unit_T>::AsSubClassRef(), max_value));
+  }
+  constexpr void Clamp(Unit_T min_value, Unit_T max_value) {
+    *this = Clamped(min_value, max_value);
+  }
+  constexpr Unit_T operator+(const Unit_T other) const {
+    if (this->IsPlusInfinity() || other.IsPlusInfinity()) {
+      RTC_DCHECK(!this->IsMinusInfinity());
+      RTC_DCHECK(!other.IsMinusInfinity());
+      return this->PlusInfinity();
+    } else if (this->IsMinusInfinity() || other.IsMinusInfinity()) {
+      RTC_DCHECK(!this->IsPlusInfinity());
+      RTC_DCHECK(!other.IsPlusInfinity());
+      return this->MinusInfinity();
+    }
+    return UnitBase<Unit_T>::FromValue(this->ToValue() + other.ToValue());
+  }
+  constexpr Unit_T operator-(const Unit_T other) const {
+    if (this->IsPlusInfinity() || other.IsMinusInfinity()) {
+      RTC_DCHECK(!this->IsMinusInfinity());
+      RTC_DCHECK(!other.IsPlusInfinity());
+      return this->PlusInfinity();
+    } else if (this->IsMinusInfinity() || other.IsPlusInfinity()) {
+      RTC_DCHECK(!this->IsPlusInfinity());
+      RTC_DCHECK(!other.IsMinusInfinity());
+      return this->MinusInfinity();
+    }
+    return UnitBase<Unit_T>::FromValue(this->ToValue() - other.ToValue());
+  }
+  constexpr Unit_T& operator+=(const Unit_T other) {
+    *this = *this + other;
+    return this->AsSubClassRef();
+  }
+  constexpr Unit_T& operator-=(const Unit_T other) {
+    *this = *this - other;
+    return this->AsSubClassRef();
+  }
+  constexpr double operator/(const Unit_T other) const {
+    return UnitBase<Unit_T>::template ToValue<double>() /
+           other.template ToValue<double>();
+  }
+  template <typename T,
+            typename std::enable_if_t<std::is_floating_point_v<T>>* = nullptr>
+  constexpr Unit_T operator/(T scalar) const {
+    return UnitBase<Unit_T>::FromValue(std::llround(this->ToValue() / scalar));
+  }
+  template <typename T,
+            typename std::enable_if_t<std::is_integral_v<T>>* = nullptr>
+  constexpr Unit_T operator/(T scalar) const {
+    return UnitBase<Unit_T>::FromValue(this->ToValue() / scalar);
+  }
+  constexpr Unit_T operator*(double scalar) const {
+    return UnitBase<Unit_T>::FromValue(std::llround(this->ToValue() * scalar));
+  }
+  constexpr Unit_T operator*(int64_t scalar) const {
+    return UnitBase<Unit_T>::FromValue(this->ToValue() * scalar);
+  }
+  constexpr Unit_T operator*(int32_t scalar) const {
+    return UnitBase<Unit_T>::FromValue(this->ToValue() * scalar);
+  }
+  constexpr Unit_T operator*(size_t scalar) const {
+    return UnitBase<Unit_T>::FromValue(this->ToValue() * scalar);
+  }
+
+ protected:
+  using UnitBase<Unit_T>::UnitBase;
+};
+
+template <class Unit_T>
+inline constexpr Unit_T operator*(double scalar, RelativeUnit<Unit_T> other) {
+  return other * scalar;
+}
+template <class Unit_T>
+inline constexpr Unit_T operator*(int64_t scalar, RelativeUnit<Unit_T> other) {
+  return other * scalar;
+}
+template <class Unit_T>
+inline constexpr Unit_T operator*(int32_t scalar, RelativeUnit<Unit_T> other) {
+  return other * scalar;
+}
+template <class Unit_T>
+inline constexpr Unit_T operator*(size_t scalar, RelativeUnit<Unit_T> other) {
+  return other * scalar;
+}
+
+template <class Unit_T>
+inline constexpr Unit_T operator-(RelativeUnit<Unit_T> other) {
+  if (other.IsPlusInfinity())
+    return UnitBase<Unit_T>::MinusInfinity();
+  if (other.IsMinusInfinity())
+    return UnitBase<Unit_T>::PlusInfinity();
+  return -1 * other;
+}
+
+}  // namespace rtc_units_impl
+
+}  // namespace webrtc
+
+#endif  // RTC_BASE_UNITS_UNIT_BASE_H_