Fix XmppLoginHandler to handle destruction from delegate methods.

remoting/signaling/xmpp_login_handler.h

 // Copyright 2015 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 REMOTING_SIGNALING_XMPP_LOGIN_HANDLER_H_
 #define REMOTING_SIGNALING_XMPP_LOGIN_HANDLER_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 17 matching lines @@
 // to send outgoing messages and calls Delegate::OnHandshakeDone() after
 // authentication is finished successfully or Delegate::OnError() on error.
 //
 // See RFC3920 for description of XMPP and authentication handshake.
 class XmppLoginHandler {
  public:
   class Delegate {
    public:
     Delegate() {}
 
+    // All Delegate methods are allowed to destroy XmppLoginHandler.
     virtual void SendMessage(const std::string& message) = 0;
     virtual void StartTls() = 0;
     virtual void OnHandshakeDone(const std::string& jid,
                                  scoped_ptr<XmppStreamParser> parser) = 0;
     virtual void OnLoginHandlerError(SignalStrategy::Error error) = 0;
 
    protected:
     virtual ~Delegate() {}
   };
 
@@ skipping 85 matching lines @@
   std::string jid_;
 
   scoped_ptr<XmppStreamParser> stream_parser_;
 
   DISALLOW_COPY_AND_ASSIGN(XmppLoginHandler);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_SIGNALING_XMPP_LOGIN_HANDLER_H_