Per discussion, implement the Omaha Client Update Protocol (CUP) in src/crypto.

google_apis/cup/client_update_protocol_openssl.cc

Index: google_apis/cup/client_update_protocol_openssl.cc
===================================================================
--- google_apis/cup/client_update_protocol_openssl.cc	(revision 0)
+++ google_apis/cup/client_update_protocol_openssl.cc	(revision 0)
@@ -0,0 +1,27 @@
+// Copyright (c) 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 "google_apis/cup/client_update_protocol.h"
+
+#include "base/logging.h"
+
+ClientUpdateProtocol::~ClientUpdateProtocol() {}
+
+bool ClientUpdateProtocol::LoadPublicKey(const base::StringPiece& public_key) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
+size_t ClientUpdateProtocol::PublicKeyLength() {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
+bool ClientUpdateProtocol::EncryptKeySource(
+    const std::vector<uint8>& key_source) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
+