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

blimp/net/client_connection_manager.cc

Index: blimp/net/client_connection_manager.cc
diff --git a/blimp/net/client_connection_manager.cc b/blimp/net/client_connection_manager.cc
index 1d513e2c73519e399f75f6218f8d046733215f7c..1e62d89f8fd10f493cf9abaf4a591c90ddfc36c9 100644
--- a/blimp/net/client_connection_manager.cc
+++ b/blimp/net/client_connection_manager.cc
@@ -7,7 +7,7 @@
 #include "base/logging.h"
 #include "blimp/common/create_blimp_message.h"
 #include "blimp/common/proto/blimp_message.pb.h"
-#include "blimp/common/protocol_version.h"
+#include "blimp/common/version_info.h"
 #include "blimp/net/blimp_connection.h"
 #include "blimp/net/blimp_message_processor.h"
 #include "blimp/net/blimp_transport.h"
@@ -68,7 +68,7 @@ void ClientConnectionManager::SendAuthenticationMessage(
     std::unique_ptr<BlimpConnection> connection) {
   DVLOG(1) << "Sending authentication message.";
   connection->GetOutgoingMessageProcessor()->ProcessMessage(
-      CreateStartConnectionMessage(client_token_, kProtocolVersion),
+      CreateStartConnectionMessage(client_token_, GetProtocolVersion()),
       base::Bind(&ClientConnectionManager::OnAuthenticationMessageSent,
                  weak_factory_.GetWeakPtr(),
                  base::Passed(std::move(connection))));