[cast_channel] Make CastMessageHandler a CastSocket::Observer instead of CastTransport::Delegate

components/cast_channel/cast_socket_service.h

 // Copyright 2017 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_CHANNEL_SERVICE_H_
 #define COMPONENTS_CAST_CHANNEL_CAST_CHANNEL_SERVICE_H_
 
 #include <map>
 #include <memory>
 
@@ skipping 18 matching lines @@
   int AddSocket(std::unique_ptr<CastSocket> socket);
 
   // Removes the CastSocket corresponding to |channel_id| from the
   // CastSocketRegistry. Returns nullptr if no such CastSocket exists.
   std::unique_ptr<CastSocket> RemoveSocket(int channel_id);
 
   // Returns the socket corresponding to |channel_id| if one exists, or nullptr
   // otherwise.
   CastSocket* GetSocket(int channel_id) const;
 
+  // Returns an observer corresponding to |id|.
+  CastSocket::Observer* GetObserver(const std::string& id);
+
+  // Adds |observer| to |socket_observer_map_| keyed by |id|.
+  void AddObserver(const std::string& id,
+                   std::unique_ptr<CastSocket::Observer> observer);
+
  private:
   ~CastSocketService() override;
 
   // RefcountedKeyedService implementation.
   void ShutdownOnUIThread() override;
 
   // Used to generate CastSocket id.
   static int last_channel_id_;
 
   // The collection of CastSocket keyed by channel_id.
   std::map<int, std::unique_ptr<CastSocket>> sockets_;
 
+  // Map of CastSocket::Observer keyed by observer id. For extension side
+  // observers, id is extension_id; For browser side observers, id is a hard
+  // coded string.
+  std::map<std::string, std::unique_ptr<CastSocket::Observer>>
+      socket_observer_map_;
+
   THREAD_CHECKER(thread_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(CastSocketService);
 };
 
 }  // namespace cast_channel
 
 #endif  // COMPONENTS_CAST_CHANNEL_CAST_CHANNEL_SERVICE_H_