pagespeed/ngx_pagespeed — pull request #474 by oschaaf (2013-08-05 08:41:26+00:00)
Title: max-buffer-size: use ngx_pagesize

Other modules seem to use ngx_pagesize as the default buffer size:
http://lxr.evanmiller.org/http/source/http/modules/ngx_http_gunzip_filter_module.c#L661