Cleanup usage of scoped_ptr<> in remoting for C++11

remoting/protocol/me2me_host_authenticator_factory.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/protocol/me2me_host_authenticator_factory.h"
 
 #include "base/base64.h"
 #include "base/strings/string_util.h"
 #include "remoting/base/rsa_key_pair.h"
 #include "remoting/protocol/channel_authenticator.h"
@@ skipping 30 matching lines @@
 
   virtual void ProcessMessage(const buzz::XmlElement* message,
                               const base::Closure& resume_callback) OVERRIDE {
     DCHECK_EQ(state_, WAITING_MESSAGE);
     state_ = REJECTED;
     resume_callback.Run();
   }
 
   virtual scoped_ptr<buzz::XmlElement> GetNextMessage() OVERRIDE {
     NOTREACHED();
-    return scoped_ptr<buzz::XmlElement>();
+    return nullptr;
   }
 
   virtual scoped_ptr<ChannelAuthenticator>
   CreateChannelAuthenticator() const OVERRIDE {
     NOTREACHED();
-    return scoped_ptr<ChannelAuthenticator>();
+    return nullptr;
   }
 
  protected:
   State state_;
 };
 
 }  // namespace
 
 // static
 scoped_ptr<AuthenticatorFactory>
@@ skipping 90 matching lines @@
     return NegotiatingHostAuthenticator::CreateWithSharedSecret(
         local_cert_, key_pair_, shared_secret_hash_.value,
         shared_secret_hash_.hash_function, pairing_registry_);
   }
 
   return scoped_ptr<Authenticator>(new RejectingAuthenticator());
 }
 
 }  // namespace protocol
 }  // namespace remoting