Revert "Eliminate all code related to the AutomaticProfileResetter."

chrome/browser/profile_resetter/jtl_foundation.cc

+// Copyright 2013 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 "chrome/browser/profile_resetter/jtl_foundation.h"
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+
+namespace jtl_foundation {
+
+Hasher::Hasher(const std::string& seed) : hmac_(crypto::HMAC::SHA256) {
+  if (!hmac_.Init(seed))
+    NOTREACHED();
+}
+
+Hasher::~Hasher() {}
+
+std::string Hasher::GetHash(const std::string& input) const {
+  if (cached_hashes_.find(input) == cached_hashes_.end()) {
+    // Calculate value.
+    unsigned char digest[kHashSizeInBytes];
+    if (!hmac_.Sign(input, digest, arraysize(digest))) {
+      NOTREACHED();
+      return std::string();
+    }
+    // Instead of using the full SHA256, we only use the hex encoding of the
+    // first 16 bytes.
+    cached_hashes_[input] = base::HexEncode(digest, kHashSizeInBytes / 2);
+    DCHECK_EQ(kHashSizeInBytes, cached_hashes_[input].size());
+  }
+  return cached_hashes_[input];
+}
+
+// static
+bool Hasher::IsHash(const std::string& maybe_hash) {
+  if (maybe_hash.size() != kHashSizeInBytes)
+    return false;
+  for (std::string::const_iterator it = maybe_hash.begin();
+       it != maybe_hash.end(); ++it) {
+    if (!IsHexDigit(*it))
+      return false;
+  }
+  return true;
+}
+
+}  // namespace jtl_foundation