Cut down on usage of deprecated APIs in //crypto.

crypto/auto_cbb.h

Index: crypto/auto_cbb.h
diff --git a/crypto/auto_cbb.h b/crypto/auto_cbb.h
new file mode 100644
index 0000000000000000000000000000000000000000..5206a214f97cc1be8ddb9622ba27648926cba350
--- /dev/null
+++ b/crypto/auto_cbb.h
@@ -0,0 +1,35 @@
+// 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.
+
+#ifndef CRYPTO_AUTO_CBB_H_
+#define CRYPTO_AUTO_CBB_H_
+
+#include <openssl/bytestring.h>
+
+#include "base/macros.h"
+
+namespace crypto {
+
+// AutoCBB is a wrapper over OpenSSL's CBB type that automatically releases
+// resources when going out of scope.
+class AutoCBB {
+ public:
+  AutoCBB() { CBB_zero(&cbb_); }
+  ~AutoCBB() { CBB_cleanup(&cbb_); }
+
+  CBB* get() { return &cbb_; }
+
+  void Reset() {
+    CBB_cleanup(&cbb_);
+    CBB_zero(&cbb_);
+  }
+
+ private:
+  CBB cbb_;
+  DISALLOW_COPY_AND_ASSIGN(AutoCBB);
+};
+
+}  // namespace crypto
+
+#endif   // CRYPTO_AUTO_CBB_H_