Update to current webrtc library

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

webrtc/api/units/timestamp.h

@@ -0,0 +1,138 @@
+/*
+ *  Copyright (c) 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 API_UNITS_TIMESTAMP_H_
+#define API_UNITS_TIMESTAMP_H_
+
+#ifdef UNIT_TEST
+#include <ostream>  // no-presubmit-check TODO(webrtc:8982)
+#endif              // UNIT_TEST
+
+#include <string>
+#include <type_traits>
+
+#include "api/units/time_delta.h"
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+// Timestamp represents the time that has passed since some unspecified epoch.
+// The epoch is assumed to be before any represented timestamps, this means that
+// negative values are not valid. The most notable feature is that the
+// difference of two Timestamps results in a TimeDelta.
+class Timestamp final : public rtc_units_impl::UnitBase<Timestamp> {
+ public:
+  template <typename T>
+  static constexpr Timestamp Seconds(T value) {
+    static_assert(std::is_arithmetic<T>::value, "");
+    return FromFraction(1'000'000, value);
+  }
+  template <typename T>
+  static constexpr Timestamp Millis(T value) {
+    static_assert(std::is_arithmetic<T>::value, "");
+    return FromFraction(1'000, value);
+  }
+  template <typename T>
+  static constexpr Timestamp Micros(T value) {
+    static_assert(std::is_arithmetic<T>::value, "");
+    return FromValue(value);
+  }
+
+  Timestamp() = delete;
+
+  template <typename T = int64_t>
+  constexpr T seconds() const {
+    return ToFraction<1000000, T>();
+  }
+  template <typename T = int64_t>
+  constexpr T ms() const {
+    return ToFraction<1000, T>();
+  }
+  template <typename T = int64_t>
+  constexpr T us() const {
+    return ToValue<T>();
+  }
+
+  constexpr int64_t seconds_or(int64_t fallback_value) const {
+    return ToFractionOr<1000000>(fallback_value);
+  }
+  constexpr int64_t ms_or(int64_t fallback_value) const {
+    return ToFractionOr<1000>(fallback_value);
+  }
+  constexpr int64_t us_or(int64_t fallback_value) const {
+    return ToValueOr(fallback_value);
+  }
+
+  constexpr Timestamp operator+(const TimeDelta delta) const {
+    if (IsPlusInfinity() || delta.IsPlusInfinity()) {
+      RTC_DCHECK(!IsMinusInfinity());
+      RTC_DCHECK(!delta.IsMinusInfinity());
+      return PlusInfinity();
+    } else if (IsMinusInfinity() || delta.IsMinusInfinity()) {
+      RTC_DCHECK(!IsPlusInfinity());
+      RTC_DCHECK(!delta.IsPlusInfinity());
+      return MinusInfinity();
+    }
+    return Timestamp::Micros(us() + delta.us());
+  }
+  constexpr Timestamp operator-(const TimeDelta delta) const {
+    if (IsPlusInfinity() || delta.IsMinusInfinity()) {
+      RTC_DCHECK(!IsMinusInfinity());
+      RTC_DCHECK(!delta.IsPlusInfinity());
+      return PlusInfinity();
+    } else if (IsMinusInfinity() || delta.IsPlusInfinity()) {
+      RTC_DCHECK(!IsPlusInfinity());
+      RTC_DCHECK(!delta.IsMinusInfinity());
+      return MinusInfinity();
+    }
+    return Timestamp::Micros(us() - delta.us());
+  }
+  constexpr TimeDelta operator-(const Timestamp other) const {
+    if (IsPlusInfinity() || other.IsMinusInfinity()) {
+      RTC_DCHECK(!IsMinusInfinity());
+      RTC_DCHECK(!other.IsPlusInfinity());
+      return TimeDelta::PlusInfinity();
+    } else if (IsMinusInfinity() || other.IsPlusInfinity()) {
+      RTC_DCHECK(!IsPlusInfinity());
+      RTC_DCHECK(!other.IsMinusInfinity());
+      return TimeDelta::MinusInfinity();
+    }
+    return TimeDelta::Micros(us() - other.us());
+  }
+  constexpr Timestamp& operator-=(const TimeDelta delta) {
+    *this = *this - delta;
+    return *this;
+  }
+  constexpr Timestamp& operator+=(const TimeDelta delta) {
+    *this = *this + delta;
+    return *this;
+  }
+
+ private:
+  friend class rtc_units_impl::UnitBase<Timestamp>;
+  using UnitBase::UnitBase;
+  static constexpr bool one_sided = true;
+};
+
+std::string ToString(Timestamp value);
+inline std::string ToLogString(Timestamp value) {
+  return ToString(value);
+}
+
+#ifdef UNIT_TEST
+inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)
+    std::ostream& stream,         // no-presubmit-check TODO(webrtc:8982)
+    Timestamp value) {
+  return stream << ToString(value);
+}
+#endif  // UNIT_TEST
+
+}  // namespace webrtc
+
+#endif  // API_UNITS_TIMESTAMP_H_