Prefetching cross-origin subresources for the current page gives double fetch

• Component: New Bugs
• Status: NEW ---

[Jeff Kaufman]

When a page makes a cross-origin prefetch it's not used on that page.  To reproduce:

1. Turn on Develop > Experimental Features > LinkPrefetch (tested in Version 14.1)
2. Visit https://www.jefftk.com/test/prefetch/prefetch-nested
3. See that bg.css, log.js, and hello-world are immediately fetched
4. After waiting five seconds, see that they are fetched a second time (confirmed with server logs)

I tried adding "as=" attributes, without effect: https://www.jefftk.com/test/prefetch/prefetch-nested-as

It looks to me like the document is used for prefetching if I navigate to it instead of putting it in an iframe (https://www.jefftk.com/test/prefetch/prefetch-navigate).  This one does make some sense: if you prefetch a document you could plausibly either want to navigate the whole page to it, or navigate an iframe.  Chrome handles this the same way as Safari, while Firefox does the opposite; I've filed https://github.com/whatwg/html/issues/6723

[Radar WebKit Bug Importer]

<rdar://problem/78878195>