about:cache is not useful anymore in ESR52-based Tor Browser (only wyciwyg-URIs if at all any)
I wanted to investigate #21689 (moved) and started to look at
about:cache output to check for isolation keys. But to my surprise there is only garbage in it (in e10s mode), meaning all URLs start with the wyciwyg scheme, or nothing at all (in non-e10s-mode).
After re-reading #9336 (moved) I suspect the cached elements are basically not showing up in e10s mode either but instead some weird wyciwyg incarnations.
Now, I tested manually that things are still cached and that cache isolation seems to be working which is a good thing. But we should investigate and fix this issue as it is highly confusing and might conceal bugs we would otherwise see.