Don't create a pairing registry on platforms that don't provide a delegate.

remoting/host/remoting_me2me_host.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.
 //
 // This file implements a standalone host process for Me2Me.
 
 #include <string>
 
 #include "base/at_exit.h"
 #include "base/bind.h"
@@ skipping 611 matching lines @@
   if (third_party_auth_config_.is_empty()) {
     scoped_refptr<PairingRegistry> pairing_registry;
     if (allow_pairing_) {
       // On Windows |pairing_registry_| is initialized in
       // InitializePairingRegistry().
 #if !defined(OS_WIN)
       if (!pairing_registry_) {
         scoped_ptr<PairingRegistry::Delegate> delegate =
             CreatePairingRegistryDelegate();
 
-        pairing_registry_ = new PairingRegistry(context_->file_task_runner(),
-                                                delegate.Pass());
+        if (delegate)
+          pairing_registry_ = new PairingRegistry(context_->file_task_runner(),
+                                                  delegate.Pass());
       }
 #endif  // defined(OS_WIN)
 
       pairing_registry = pairing_registry_;
     }
 
     factory = protocol::Me2MeHostAuthenticatorFactory::CreateWithSharedSecret(
         use_service_account_, host_owner_, local_certificate, key_pair_,
         host_secret_hash_, pairing_registry);
 
@@ skipping 896 matching lines @@
       base::TimeDelta::FromSeconds(kShutdownTimeoutSeconds));
   new HostProcess(context.Pass(), &exit_code, &shutdown_watchdog);
 
   // Run the main (also UI) message loop until the host no longer needs it.
   message_loop.Run();
 
   return exit_code;
 }
 
 }  // namespace remoting