Guest mode says "Pages you view in this window won’t appear in the browser history and they won’t leave other traces, like cookies, on the computer after you close all open Guest windows. Any files you download will be preserved, however."

Trying with the provided URL localstorage seems to get cleared (when exiting guest mode), but IndexedDB and WebSQL indeed do seem to not get cleared.

dullweber: This seems like something you would care and/or know about?

AFAIU, Guest mode is Incognito atop of an empty regular profile. All web-facing storage should be discarded the same way as it is in Incognito.

According to the report, this works on closing Chrome, but not the window itself. I assume that closing all guest windows doesn't destroy the Guest profile? That sounds like a bug in the Profiles codebase rather than browsing data.

+bauerb@, do you know something about this? We had a setting "Continue running background apps..." which used to prolong the lifetime of profiles. AFAICT it doesn't exist anymore though, and it would certainly be unexpected in the Guest mode.

This is happening on Linux as well, so I don't think there is anything Mac specific.
When a Guest window is closed it doesn't go throught he normal incognito cleanup flow but uses BrowsingDataRemover instead. https://cs.chromium.org/chromium/src/chrome/browser/ui/browser.cc?l=560&rcl=3e0dea7b74b85a1ff9ffe5493098650443328010

Maybe the incognito implementation of WebSQL and IndexedDB don't implement deletions correctly?
I also think that this bug is quite important as a promise of Guest mode doesn't work correctly.

The code linked in #7 answers my question from #6 about why this behaves differently than just closing Incognito. However, it seems that the implementation is based on BrowsingDataRemover, which is not correct, as there is no guarantee that BrowsingDataRemover is aware about every piece of data.

It seems that the correct solution would be to:
1. Destroy the Profile (and recreate in the next guest session), to ensure that we delete all in-memory data same way as in Incognito.
2. Also delete the directory backing the profile.

So while this particular issue could be caused by WebSQL and IndexedDB not implementing deletion correctly in Incognito, it also uncovered a larger problem in the design of the guest mode.

bauerb@, msarda@ - do you have any background about why the guest mode was implemented this way?

rhalavati@ FYI as well

It looks like there was some work on fixing Guest mode deletion but it wasn't finished:  https://crbug.com/445036#c26 

Using devtools from Application>Clear Storage in incognito mode also doesn't remove websql and indexed db data. I will file a separate bug as it affects devtools and probably also ClearSiteData

IIRC, the issue was that (non-incognito) Profile objects aren't destroyed until browser shutdown for some reason, so if a guest profile is closed, we just try to delete browsing data instead. I was not particularly involved with this code though.

Assigning to rhalavati@, as we discussed today.

--Chrome Identity automated triaging--

This bug is P0 or P1 and has gone two weeks without any activity. Please provide a status update or lower the priority. Please see https://goo.gl/78kbny for more details. Please remove the Services>SignIn or UI>Browser>Profiles components if this bug isn't related to Chrome Identity.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Should this still be marked as P1, or should we downgrade it to P2 since it hasn't been updated for a couple of months?

I've put it in my next week ToDo list.

Does this have the same root cause as  issue 876659  by any chance?

Yeah, seems to be the same root cause as  issue 876659  - the issue with IndexedDB is fixed on ToT, WebSQL still broken. :)