Devlin: Is it deliberate that we don't show any kind of warnings/errors for packed extensions (kDefaultMask is 0, see https://cs.chromium.org/chromium/src/chrome/browser/extensions/error_console/error_console.cc?sq=package:chromium&g=0&l=44)

More-or-less intentional.  We don't want these to show up for the average user, and pre-error console there wasn't a good way to have users opt-in to them, so we used whether the extension was unpacked.  Now, we could probably tie these in with whether "Collect errors" is enabled for the extension, but we haven't done so yet.  I'd be supportive of making that change.

Thanks, I'll limit the scope of the bug then.