Implement CUP signing in UpdateClient.

components/update_client/client_update_protocol_ecdsa.h

 // 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 COMPONENTS_UPDATE_CLIENT_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
 #define COMPONENTS_UPDATE_CLIENT_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_piece.h"
 
+namespace update_client {
+
 // Client Update Protocol v2, or CUP-ECDSA, is used by Google Update (Omaha)
 // servers to ensure freshness and authenticity of update checks over HTTP,
 // without the overhead of HTTPS -- namely, no PKI, no guarantee of privacy,
 // and no request replay protection (since update checks are idempotent).
 //
 // CUP-ECDSA relies on a single signing operation using ECDSA with SHA-256,
 // instead of the original CUP which used HMAC-SHA1 with a random signing key
 // encrypted using RSA.
 //
 // Each ClientUpdateProtocolEcdsa object represents a single update check in
@@ skipping 48 matching lines @@
   // SignRequest(), and checked by ValidateResponse().
   std::vector<uint8_t> request_hash_;
 
   // The query string containing key version and nonce in UTF-8 form.  This is
   // modified on each call to SignRequest(), and checked by ValidateResponse().
   std::string request_query_cup2key_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ClientUpdateProtocolEcdsa);
 };
 
+}  // namespace update_client
+
 #endif  // COMPONENTS_UPDATE_CLIENT_CLIENT_UPDATE_PROTOCOL_ECDSA_H_