As you may be aware, Windows uses the key combination Alt+Shift to change the active input language. Google Chrome doesn't invoke this key combination, does it?
As far as I know, automatically changing the input language (e.g. in a text entry box) isn't part of any approved web platform.
I'm aware of the Alt+Shift combination, and I'm forced to use it to get my keyboard layout back - but this combination shouldn't do anything if there's only a single layout installed (one of the reasons why I always make sure that I don't have US layout installed is to prevent applications switching to it - unfortunately, it seems that even if it's not installed, some programs will switch to this layout on Windows 7 anyway, which is very annoying). And the switch happens without pressing Alt+Shift.