Handle certificate generation errors in chromoting host.

remoting/host/host_key_pair.cc

 // Copyright (c) 2012 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 "remoting/host/host_key_pair.h"
 
 #include <limits>
 #include <string>
 #include <vector>
 
@@ skipping 87 matching lines @@
   CHECK(key_->ExportPrivateKey(&key_bytes));
   return crypto::RSAPrivateKey::CreateFromPrivateKeyInfo(key_bytes);
 }
 
 std::string HostKeyPair::GenerateCertificate() const {
   scoped_refptr<net::X509Certificate> cert =
       net::X509Certificate::CreateSelfSigned(
           key_.get(), "CN=chromoting",
           base::RandInt(1, std::numeric_limits<int>::max()),
           base::TimeDelta::FromDays(1));
+  if (!cert)
+    return std::string();
+
   std::string encoded;
   bool result = net::X509Certificate::GetDEREncoded(cert->os_cert_handle(),
                                                     &encoded);
   CHECK(result);
   return encoded;
 }
 
 }  // namespace remoting