Add base::UnguessableToken

base/nonce.cc

Index: base/nonce.cc
diff --git a/base/nonce.cc b/base/nonce.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bf147aa421248b03defb9a51b31f58267a01cddb
--- /dev/null
+++ b/base/nonce.cc
@@ -0,0 +1,31 @@
+// Copyright 2016 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 "base/nonce.h"
+
+#include "base/format_macros.h"
+#include "base/rand_util.h"
+#include "base/strings/stringprintf.h"
+
+namespace base {
+Nonce::Nonce(uint64_t high, uint64_t low) : high_(high), low_(low) {}
+
+std::string Nonce::ToString() const {
+  return base::StringPrintf("(%" PRIu64 ":%" PRIu64 ")", high_, low_);
+}
+
+// Static
+Nonce Nonce::Generate() {
+  Nonce nonce;
+  // Use base::RandBytes instead of crypto::RandBytes, because crypto calls the
+  // base version directly, and to prevent the dependency from base/ to crypto/.
+  base::RandBytes(&nonce, sizeof(nonce));
+  return nonce;
+}
+
+// Static
+Nonce Nonce::Deserialize(uint64_t high, uint64_t low) {
+  return Nonce(high, low);
+}
+}  // namespace base