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

extensions/browser/api/cast_channel/cast_channel_api.h

Index: extensions/browser/api/cast_channel/cast_channel_api.h
diff --git a/extensions/browser/api/cast_channel/cast_channel_api.h b/extensions/browser/api/cast_channel/cast_channel_api.h
index baecc333a8db04baa8a3b5176afba35fbf722386..4453a791fab98561da5556b83248c82a5092a864 100644
--- a/extensions/browser/api/cast_channel/cast_channel_api.h
+++ b/extensions/browser/api/cast_channel/cast_channel_api.h
@@ -134,26 +134,24 @@ class CastChannelOpenFunction : public CastChannelAsyncApiFunction {
   //     Parameter #0 is a scoped pointer to the event payload.
   using EventDispatchCallback = base::Callback<void(std::unique_ptr<Event>)>;
 
-  // Receives incoming messages and errors and provides additional API and
-  // origin socket context.
-  class CastMessageHandler : public cast_channel::CastTransport::Delegate {
+  // Receives incoming messages and errors and provides additional API context.
+  class CastMessageHandler : public cast_channel::CastSocket::Observer {
    public:
     CastMessageHandler(const EventDispatchCallback& ui_dispatch_cb,
-                       cast_channel::CastSocket* socket,
                        scoped_refptr<cast_channel::Logger> logger);
     ~CastMessageHandler() override;
 
-    // CastTransport::Delegate implementation.
-    void OnError(cast_channel::ChannelError error_state) override;
-    void OnMessage(const cast_channel::CastMessage& message) override;
-    void Start() override;
+    // CastSocket::Observer implementation.
+    void OnError(const cast_channel::CastSocket& socket,
+                 cast_channel::ChannelError error_state) override;
+    void OnMessage(const cast_channel::CastSocket& socket,
+                   const cast_channel::CastMessage& message) override;
 
    private:
     // Callback for sending events to the extension.
     // Should be bound to a weak pointer, to prevent any use-after-free
     // conditions.
     EventDispatchCallback const ui_dispatch_cb_;
-    cast_channel::CastSocket* const socket_;
     // Logger object for reporting error details.
     scoped_refptr<cast_channel::Logger> logger_;