Fix crash when user disconnects It2Me host

remoting/signaling/delegating_signal_strategy.h

 // Copyright 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.
 
 #ifndef REMOTING_CLIENT_PLUGIN_DELEGATING_SIGNAL_STRATEGY_H_
 #define REMOTING_CLIENT_PLUGIN_DELEGATING_SIGNAL_STRATEGY_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list_threadsafe.h"
 #include "remoting/signaling/signal_strategy.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }  // namespace base
 
 namespace remoting {
 
 // A signaling strategy class that delegates IQ sending and receiving.
 //
 // Notes on thread safety:
 // 1. This object can be created on any thread.
-// 2. OnIncomingMessage() must be called on the same thread on which this object
-//    is created.
-// 3. |send_iq_callback| will always be called on the thread that it is created.
+// 2. |send_iq_callback| will always be called on the thread that it is created.
 //    Note that |send_iq_callback| may be called after this object is destroyed.
-// 4. The caller should invoke all methods on the SignalStrategy interface on
+// 3. The caller should invoke all methods on the SignalStrategy interface on
 //    the |client_task_runner|.
-// 5. All listeners will be called on |client_task_runner| as well.
-// 6. The destructor should always be called on the |client_task_runner|.
+// 4. All listeners will be called on |client_task_runner| as well.
+// 5. The destructor should always be called on the |client_task_runner|.
+// 6. As a result of (5), use MakeIncomingMessageCallback() to obtain a callback
+//    when passing incoming signaling messages from the delegate.
 class DelegatingSignalStrategy : public SignalStrategy {
  public:
-  typedef base::Callback<void(const std::string&)> SendIqCallback;
+  typedef base::Callback<void(const std::string&)> IqCallback;

[Sergey Ulanov, 2017/03/14 19:20:59]

Please use base::RepeatingCallback instead of base::Callback

(Callback is being replaced with OnceCallback and RepeatingCallback. There are
some details
onhttps://chromium.googlesource.com/chromium/src/+/master/docs/callback.md)

[kelvinp, 2017/03/15 21:56:46]

Done.

 
   DelegatingSignalStrategy(
       std::string local_jid,
       scoped_refptr<base::SingleThreadTaskRunner> client_task_runner,
-      const SendIqCallback& send_iq_callback);
+      const IqCallback& send_iq_callback);
   ~DelegatingSignalStrategy() override;
 
-  void OnIncomingMessage(const std::string& message);
+  IqCallback MakeIncomingMessageCallback();

[Sergey Ulanov, 2017/03/14 19:20:59]

s/Make/Get/

(potentially this function could just return a callback it already has, it
doesn't need to "make" a new callback every time)

 
   // SignalStrategy interface.
   void Connect() override;
   void Disconnect() override;
   State GetState() const override;
   Error GetError() const override;
   std::string GetLocalJid() const override;
   void AddListener(Listener* listener) override;
   void RemoveListener(Listener* listener) override;
   bool SendStanza(std::unique_ptr<buzz::XmlElement> stanza) override;
   std::string GetNextId() override;
 
  private:
+  static void OnIncomingMessageFromDelegate(
+      base::WeakPtr<DelegatingSignalStrategy> weak_ptr,
+      scoped_refptr<base::SingleThreadTaskRunner> client_task_runner,
+      const std::string& message);
+
+  void OnIncomingMessage(const std::string& message);
+
   std::string local_jid_;
   scoped_refptr<base::SingleThreadTaskRunner> delegate_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> client_task_runner_;
 
-  SendIqCallback send_iq_callback_;
+  IqCallback send_iq_callback_;
   base::ObserverList<Listener> listeners_;
 
   base::WeakPtrFactory<DelegatingSignalStrategy> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DelegatingSignalStrategy);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_PLUGIN_DELEGATING_SIGNAL_STRATEGY_H_