Enables delegating signal strategy for 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/observer_list.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() and |send_iq_callback| will always be called on the

[Sergey Ulanov, 2016/10/06 18:28:57]

Suggest separating this statement into two. |send_iq_callback| is called by this
class, while  OnIncomingMessage() will be called by the client. I.e. add a new
item between (2) and (3): OnIncomingMessage() must be called on the same same
thread on which this object is created.

[kelvinp, 2016/10/06 20:30:28]

Done.

+//    thread that it is created on. Note that |send_iq_callback| may be called
+//    after the instance is destroyed.
+// 3. The caller should invoke all methods on the |client_task_runner|.

[Sergey Ulanov, 2016/10/06 18:28:57]

Maybe rephrase this as "SignalStrategy interface must be used on
|client_task_runner|."

[kelvinp, 2016/10/06 20:30:28]

Done.

+// 4. All listeners will be called on |client_task_runner| as well.
+// 5. The destructor should always be called on the |client_task_runner|.
 class DelegatingSignalStrategy : public SignalStrategy {
  public:
   typedef base::Callback<void(const std::string&)> SendIqCallback;
 
-  DelegatingSignalStrategy(std::string local_jid,
-                       const SendIqCallback& send_iq_callback);
+  DelegatingSignalStrategy(
+      std::string local_jid,
+      scoped_refptr<base::SingleThreadTaskRunner> client_task_runner,
+      const SendIqCallback& send_iq_callback);
   ~DelegatingSignalStrategy() override;
 
   void OnIncomingMessage(const std::string& message);
 
   // 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:
   std::string local_jid_;
+  scoped_refptr<base::SingleThreadTaskRunner> delegate_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> client_task_runner_;
+
   SendIqCallback send_iq_callback_;
+  base::ObserverList<Listener> listeners_;
 
-  base::ObserverList<Listener> listeners_;
+  base::WeakPtrFactory<DelegatingSignalStrategy> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DelegatingSignalStrategy);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_PLUGIN_DELEGATING_SIGNAL_STRATEGY_H_