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diff --git a/tests/third_party/libvpx/acm_random.h b/tests/third_party/libvpx/acm_random.h
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+++ b/tests/third_party/libvpx/acm_random.h
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+/*
+ *  Copyright (c) 2012 The WebM 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 LIBGAV1_TESTS_THIRD_PARTY_LIBVPX_ACM_RANDOM_H_
+#define LIBGAV1_TESTS_THIRD_PARTY_LIBVPX_ACM_RANDOM_H_
+
+#include <cassert>
+#include <cstdint>
+#include <limits>
+
+#include "gtest/gtest.h"
+
+namespace libvpx_test {
+
+class ACMRandom {
+ public:
+  ACMRandom() : random_(DeterministicSeed()) {}
+
+  explicit ACMRandom(int seed) : random_(seed) {}
+
+  void Reset(int seed) { random_.Reseed(seed); }
+  uint16_t Rand16(void) {
+    const uint32_t value =
+        random_.Generate(testing::internal::Random::kMaxRange);
+    return (value >> 15) & 0xffff;
+  }
+
+  int32_t Rand20Signed(void) {
+    // Use 20 bits: values between 524287 and -524288.
+    const uint32_t value = random_.Generate(1048576);
+    return static_cast<int32_t>(value) - 524288;
+  }
+
+  int16_t Rand16Signed(void) {
+    // Use 16 bits: values between 32767 and -32768.
+    return static_cast<int16_t>(random_.Generate(65536));
+  }
+
+  int16_t Rand13Signed(void) {
+    // Use 13 bits: values between 4095 and -4096.
+    const uint32_t value = random_.Generate(8192);
+    return static_cast<int16_t>(value) - 4096;
+  }
+
+  int16_t Rand9Signed(void) {
+    // Use 9 bits: values between 255 (0x0FF) and -256 (0x100).
+    const uint32_t value = random_.Generate(512);
+    return static_cast<int16_t>(value) - 256;
+  }
+
+  uint8_t Rand8(void) {
+    const uint32_t value =
+        random_.Generate(testing::internal::Random::kMaxRange);
+    // There's a bit more entropy in the upper bits of this implementation.
+    return (value >> 23) & 0xff;
+  }
+
+  uint8_t Rand8Extremes(void) {
+    // Returns a random value near 0 or near 255, to better exercise
+    // saturation behavior.
+    const uint8_t r = Rand8();
+    return static_cast<uint8_t>((r < 128) ? r << 4 : r >> 4);
+  }
+
+  uint32_t RandRange(const uint32_t range) {
+    // testing::internal::Random::Generate provides values in the range
+    // testing::internal::Random::kMaxRange.
+    assert(range <= testing::internal::Random::kMaxRange);
+    return random_.Generate(range);
+  }
+
+  int PseudoUniform(int range) { return random_.Generate(range); }
+
+  int operator()(int n) { return PseudoUniform(n); }
+
+  static constexpr int DeterministicSeed(void) { return 0xbaba; }
+
+ private:
+  testing::internal::Random random_;
+};
+
+}  // namespace libvpx_test
+
+#endif  // LIBGAV1_TESTS_THIRD_PARTY_LIBVPX_ACM_RANDOM_H_