Update to current webrtc library

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

webrtc/rtc_base/numerics/safe_conversions.h

@@ -0,0 +1,76 @@
+/*
+ *  Copyright 2014 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.
+ */
+
+// Borrowed from Chromium's src/base/numerics/safe_conversions.h.
+
+#ifndef RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
+#define RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
+
+#include <limits>
+
+#include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_conversions_impl.h"
+
+namespace rtc {
+
+// Convenience function that returns true if the supplied value is in range
+// for the destination type.
+template <typename Dst, typename Src>
+inline constexpr bool IsValueInRangeForNumericType(Src value) {
+  return internal::RangeCheck<Dst>(value) == internal::TYPE_VALID;
+}
+
+// checked_cast<> and dchecked_cast<> are analogous to static_cast<> for
+// numeric types, except that they [D]CHECK that the specified numeric
+// conversion will not overflow or underflow. NaN source will always trigger
+// the [D]CHECK.
+template <typename Dst, typename Src>
+inline constexpr Dst checked_cast(Src value) {
+  RTC_CHECK(IsValueInRangeForNumericType<Dst>(value));
+  return static_cast<Dst>(value);
+}
+template <typename Dst, typename Src>
+inline constexpr Dst dchecked_cast(Src value) {
+  RTC_DCHECK(IsValueInRangeForNumericType<Dst>(value));
+  return static_cast<Dst>(value);
+}
+
+// saturated_cast<> is analogous to static_cast<> for numeric types, except
+// that the specified numeric conversion will saturate rather than overflow or
+// underflow. NaN assignment to an integral will trigger a RTC_CHECK condition.
+template <typename Dst, typename Src>
+inline constexpr Dst saturated_cast(Src value) {
+  // Optimization for floating point values, which already saturate.
+  if (std::numeric_limits<Dst>::is_iec559)
+    return static_cast<Dst>(value);
+
+  switch (internal::RangeCheck<Dst>(value)) {
+    case internal::TYPE_VALID:
+      return static_cast<Dst>(value);
+
+    case internal::TYPE_UNDERFLOW:
+      return std::numeric_limits<Dst>::min();
+
+    case internal::TYPE_OVERFLOW:
+      return std::numeric_limits<Dst>::max();
+
+    // Should fail only on attempting to assign NaN to a saturated integer.
+    case internal::TYPE_INVALID:
+      FATAL();
+      return std::numeric_limits<Dst>::max();
+  }
+
+  FATAL();
+  return static_cast<Dst>(value);
+}
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_