Gracefully handle lack of IndexedDB in Firefox Private browsing

[jeffgca]

Summary

There is no IndexedDB in Firefox Private Windows, but we need it, so we fail eg on loading drive.fission.codes

Problem

Firefox doesn't allow IndexedDB in Private Windows. They hopefully eventually will, the relevant Firefox bug is:

https://bugzilla.mozilla.org/show_bug.cgi?id=1639542

Impact

People who want to use drive in a private window, cannot currently. Drive works fine in Chrome's incognito mode.

Solution

When we feature-detect for IndexedDB the user experience on Drive currently is an infinite spinner, and as well a console message that doesn't give us much info. We should replace this with a link to documentation on browser compatibility that we can maintain outside this repo.

Detail

To Reproduce
Steps to reproduce the behavior:
0. Open Firefox

1. Go to drive.fission.codes

Expected behavior

Drive should work as expected.

Screenshots

Desktop (please complete the following information):

• OS: macOS 10.15.latest
• Browser Firefox
• Version 88

Additional context

It remains to be seen whether Firefox will ever fix this bug, traffic seems stagnant despite apparently there being problems with Netflix:

( Now, Netflix's error is also not quite right, updating will not fix the issue. )

[jeffgca]

More on this: I sent an email to someone on the Gecko team and they said that this will be fixed in Firefox ( as will a related issue affecting service workers ) but that it may take some time as it is blocked on lower level feature work. IMO the right thing experience for us currently is:

1. try to detect this situation and direct users to a statement about browser / browsing mode support in a generic way that can fit with any app developer's flows

2. try to ensure that when this starts working in Firefox it also automagically starts working for fission apps

3. draft and maintain docs for developers and and users about browser support.

[icidasset]

Thanks Jeff! That "unsupported_browser" error is a generic webnative thing, which is documented. We just didn't handle it yet in Drive, since it's a relatively new addition. I'll be adding a proper error screen here.

---

Workaround to use Drive in Firefox's private mode, set the following to true in about:config

dom.indexedDB.privateBrowsing.enabled

[icidasset]

Now shows a proper error page.
Will keep the issue open, since I still need to make it a little nicer and add more information & links.