In 95a82d608d, we lowered the default for
`Onebox.options.max_download_kb` from 10mb to 2mb for security hardening
purposes. However, this resulted in multiple bug reports where seemingly
nomral URLs stopped being oneboxed. It turns out that lowering
`Onebox.options.max_download_kb` resulted in `Onebox::Helpers::DownloadTooLarge` being raised
more often for more URLs in `Onebox::Helpers.fetch_response` which
`Onebox::Helpers.fetch_html_doc` relies on. When
`Onebox::Helpers::DownloadTooLarge` is raised in
`Onebox::Helpers.fetch_response`, we throw away whatever response body
which we have already downloaded at that point. This is not ideal
because Nokogiri can parse incomplete HTML documents and there is a
really high chance that the incomplete HTML document still contains the
information which we need for oneboxing.
Therefore, this commit updates `Onebox::Helpers.fetch_html_doc` to not
throw away the response body when the size of the response body exceeds
`Onebox.options.max_download_size`. Instead, we just take whatever
response which we have and get Nokogiri to parse it.
c8da2a33e8