[cast_channel] Make CastSocketService a global leaky singleton

components/cast_channel/cast_socket.h

 // Copyright 2014 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 COMPONENTS_CAST_CHANNEL_CAST_SOCKET_H_
 #define COMPONENTS_CAST_CHANNEL_CAST_SOCKET_H_
 
 #include <stdint.h>
 
 #include <queue>
@@ skipping 111 matching lines @@
   // event of an error.
   // Setting the error state does not close the socket if it is open.
   virtual void SetErrorState(ChannelError error_state) = 0;
 
   // Returns a pointer to the socket's message transport layer. Can be used to
   // send and receive CastMessages over the socket.
   virtual CastTransport* transport() const = 0;
 
   // Registers |observer| with the socket to receive messages and error events.
   virtual void AddObserver(Observer* observer) = 0;
+
+  // Unregisters |observer|

[mark a. foltz, 2017/07/10 20:43:05]

Nit: Add period at end.

[zhaobin, 2017/07/12 21:58:08]

Done.

+  virtual void RemoveObserver(Observer* observer) = 0;
 };
 
 // This class implements a channel between Chrome and a Cast device using a TCP
 // socket with SSL.  The channel may authenticate that the receiver is a genuine
 // Cast device.  All CastSocketImpl objects must be used only on the IO thread.
 //
 // NOTE: Not called "CastChannel" to reduce confusion with the generated API
 // code.
 class CastSocketImpl : public CastSocket {
  public:
@@ skipping 32 matching lines @@
   CastTransport* transport() const override;
   void Close(const net::CompletionCallback& callback) override;
   const net::IPEndPoint& ip_endpoint() const override;
   int id() const override;
   void set_id(int channel_id) override;
   ReadyState ready_state() const override;
   ChannelError error_state() const override;
   bool keep_alive() const override;
   bool audio_only() const override;
   void AddObserver(Observer* observer) override;
+  void RemoveObserver(Observer* observer) override;
 
  protected:
   // CastTransport::Delegate methods for receiving handshake messages.
   class AuthTransportDelegate : public CastTransport::Delegate {
    public:
     explicit AuthTransportDelegate(CastSocketImpl* socket);
 
     // Gets the error state of the channel.
     // Returns CHANNEL_ERROR_NONE if no errors are present.
     ChannelError error_state() const;
@@ skipping 221 matching lines @@
   AuthTransportDelegate* auth_delegate_;
 
   // List of socket observers.
   base::ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(CastSocketImpl);
 };
 }  // namespace cast_channel
 
 #endif  // COMPONENTS_CAST_CHANNEL_CAST_SOCKET_H_