Set default queue size to 2.

This is to allow detection of client disconnection.

Author: patrickcjh

include/web_video_server/multipart_stream.h

@@ -13,7 +13,7 @@ class MultipartStream {
 public:
   MultipartStream(async_web_server_cpp::HttpConnectionPtr& connection,
                   const std::string& boundry="boundarydonotcross",
-                  std::size_t max_queue_size=1);
+                  std::size_t max_queue_size=2);
 
   void sendInitialHeader();
   void sendPartHeader(const ros::Time &time, const std::string& type, size_t payload_size);