Decouple Blimp transport output from BlimpConnections using MessagePort.

blimp/net/blimp_connection.h

Index: blimp/net/blimp_connection.h
diff --git a/blimp/net/blimp_connection.h b/blimp/net/blimp_connection.h
index 51070d0c7665ab9b74685f6577dc41489b5c28e2..10450d0a2853b79f13282138a717f267136df8bc 100644
--- a/blimp/net/blimp_connection.h
+++ b/blimp/net/blimp_connection.h
@@ -17,16 +17,13 @@ namespace blimp {
 class BlimpMessageProcessor;
 class BlimpMessagePump;
 class BlimpMessageSender;
-class PacketReader;
-class PacketWriter;
+class MessagePort;
 
 // Encapsulates the state and logic used to exchange BlimpMessages over
 // a network connection.
 class BLIMP_NET_EXPORT BlimpConnection : public ConnectionErrorObserver {
  public:
-  BlimpConnection(std::unique_ptr<PacketReader> reader,
-                  std::unique_ptr<PacketWriter> writer);
-
+  explicit BlimpConnection(std::unique_ptr<MessagePort> message_port);
   ~BlimpConnection() override;
 
   // Adds |observer| to the connection's error observer list.
@@ -53,9 +50,8 @@ class BLIMP_NET_EXPORT BlimpConnection : public ConnectionErrorObserver {
   void OnConnectionError(int error) override;
 
  private:
-  std::unique_ptr<PacketReader> reader_;
+  std::unique_ptr<MessagePort> message_port_;
   std::unique_ptr<BlimpMessagePump> message_pump_;
-  std::unique_ptr<PacketWriter> writer_;
   std::unique_ptr<BlimpMessageSender> outgoing_msg_processor_;
   base::ObserverList<ConnectionErrorObserver> error_observers_;
   std::unique_ptr<EndConnectionFilter> end_connection_filter_;