[whatwg] Prefetch issues

[Eric Schurman]

As described, the link prefetching capability seems to have some
limitations that work counter to the performance of the page using it.

It appears as though LINK elements are metadata elements and that
these may only be supported inside the HEAD of the document. If so,
then this is an issue in the real world, because at the time a web
server flushes chunks containing the HEAD section of a document, the
links we would want to prefetch are often not known. This is true for
all the large sites I've analyzed or worked at. For example, many
pages on a site will contain the same visual header, and we want to
flush the HEAD and visual header content while the server is in the
process of figuring out what the content of the page will be - which
will contain the links we'd like to prefetch.

Am I reading this correctly? Or is there a something that would allow
the flushing scenario I describe above?

One of the simplest approaches may be to add support for
rel="prefetch" to A and AREA's, but it's been explicitly excluded from
those. Why?

Another approach could be to allow LINK throughout the document. This
would allow for prefetching content like images even if you didn't
know them at HEAD rendering time.

Any opinions?