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..54f6b8dfbdebd8edded003d407f3ddf2c9f0f31c
--- /dev/null
+++ b/base/nonce.cc
@@ -0,0 +1,17 @@
+// 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/rand_util.h"
+
+namespace base {
+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;
+}
+}  // namespace base