Decouple Blimp transport output from BlimpConnections using MessagePort.

blimp/net/test_common.cc

Index: blimp/net/test_common.cc
diff --git a/blimp/net/test_common.cc b/blimp/net/test_common.cc
index f6b355866840edf3c8af75878e83d41f031f2d6d..f72ed236b002ea7aa902abe657baa405bd63aee1 100644
--- a/blimp/net/test_common.cc
+++ b/blimp/net/test_common.cc
@@ -11,6 +11,7 @@
 #include "blimp/common/proto/blimp_message.pb.h"
 #include "blimp/net/blimp_connection.h"
 #include "blimp/net/common.h"
+#include "blimp/net/message_port.h"
 #include "net/base/io_buffer.h"
 
 namespace blimp {
@@ -23,8 +24,8 @@ MockTransport::MockTransport() {}
 
 MockTransport::~MockTransport() {}
 
-std::unique_ptr<BlimpConnection> MockTransport::TakeConnection() {
-  return base::WrapUnique(TakeConnectionPtr());
+std::unique_ptr<MessagePort> MockTransport::TakeMessagePort() {
+  return base::WrapUnique(TakeMessagePortPtr());
 }
 
 const char* MockTransport::GetName() const {