Copying from 
https://launchpad.net/distros/ubuntu/+source/gnome-screensaver/+bug/49222/

The screensaver password dialog, that is produced whenever you want to resume
your work after a screensaver (or hibernate etc), does not indicate which
keyboard layout is active. As I use several ones at the same time, I find it
hard to know which layout is supposed to be active in GDM, and often I don't
even remember which one I used last. There is no way of finding out the layout
as the only thing showing is black dots in the input field.

This "bug" have made me loose work due to that I cannot enter my password at
times, even though I thought I correctly guessed different layouts. I do run
two different types of Dvorak on my Qwerty keyboard, so it is not easy to
guess.

Proposal:
* At least a keyboard indicator and switcher as can be seen in Gnome Panel
should be present in the password dialog.
* Possibly also a field where one can test a layout (but not in the dialog
itself, perhaps as a button) to see if it is the one expected.