Document http_chunk_size

youtube_dl/downloader/common.py

@@ -49,6 +49,9 @@ class FileDownloader(object):
     external_downloader_args:  A list of additional command-line arguments for the
                         external downloader.
     hls_use_mpegts:     Use the mpegts container for HLS videos.
+    http_chunk_size:    Size of a chunk for chunk-based HTTP downloading.May be
+                        useful for bypassing bandwidth throttling imposed by
+                        a webserver (experimental)
 
     Subclasses of this one must re-define the real_download method.
     """