Reland "Cut down /crypto and switch what is left of it to boringssl".

crypto/secure_util.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "crypto/secure_util.h"
-
-namespace crypto {
-
-bool SecureMemEqual(const void* s1, const void* s2, size_t n) {
-  const unsigned char* s1_ptr = reinterpret_cast<const unsigned char*>(s1);
-  const unsigned char* s2_ptr = reinterpret_cast<const unsigned char*>(s2);
-  unsigned char tmp = 0;
-  for (size_t i = 0; i < n; ++i, ++s1_ptr, ++s2_ptr)
-    tmp |= *s1_ptr ^ *s2_ptr;
-  return (tmp == 0);
-}
-
-}  // namespace crypto
-