Replace RE2 import with a dependency

third_party/re2/util/random.h

-// Copyright 2005-2009 The RE2 Authors.  All Rights Reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Modified from Google perftools's tcmalloc_unittest.cc.
-
-#ifndef RE2_UTIL_RANDOM_H__
-#define RE2_UTIL_RANDOM_H__
-
-#include "util/util.h"
-
-namespace re2 {
-
-// ACM minimal standard random number generator.  (re-entrant.)
-class ACMRandom {
- public:
-  ACMRandom(int32 seed) : seed_(seed) {}
-  int32 Next();
-  int32 Uniform(int32);
-
-  void Reset(int32 seed) { seed_ = seed; }
-
- private:
-  int32 seed_;
-};
-
-}  // namespace re2
-
-#endif  // RE2_UTIL_RANDOM_H__