Should "ignore higher-layer caching" flag get a definition? #8546
Description
I'm not really understanding how the "ignore higher-layer caching" flag is supposed to work actually. It seems to be functioning the exact opposite way that I'd expect. I'd expect it to be "unset" always (so we use the cache), unless some Cache-Control header directed otherwise, and I'd expect when it finally gets set, the UA would just remove it from the list of available images. But (1) it never seems to be unset ever (it looks like ever place we add to the list of available images, we set the flag), and (2) we never seem to actually modify our behavior based off of it? I could be missing something obvious, but maybe it would be good to file a separate bug about that or something, to see if anyone knows the history around it.
Originally posted by @domfarolino in #8524 (comment)
The spec is not very clear about what it means and how it clearly interacts with images keys store for a Document.