Use Chromium BUILD to approximate Blimp protocol version, and check it.

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 a662c4e10ef5d488ef5352ae3b2d1c555f66c030..52f15ffeb98183b8b1bfeec7e51026f25e0b7650 100644
--- a/blimp/net/blimp_connection.h
+++ b/blimp/net/blimp_connection.h
@@ -43,6 +43,9 @@ class BLIMP_NET_EXPORT BlimpConnection : public ConnectionErrorObserver {
   virtual BlimpMessageProcessor* GetOutgoingMessageProcessor();
 
  protected:
+  class EndConnectionHandler;
+  friend class EndConnectionHandler;
+
   BlimpConnection();
 
   // ConnectionErrorObserver implementation.
@@ -54,6 +57,7 @@ class BLIMP_NET_EXPORT BlimpConnection : public ConnectionErrorObserver {
   std::unique_ptr<PacketWriter> writer_;
   std::unique_ptr<BlimpMessageProcessor> outgoing_msg_processor_;
   base::ObserverList<ConnectionErrorObserver> error_observers_;
+  std::unique_ptr<EndConnectionHandler> end_connection_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(BlimpConnection);
 };