We should switch the keyboard layout to the layout the user set according to

chromeos/ime/input_methods.txt

 # The list of input methods that we support. The input methods metadata is
 # also defined here. We use this data for the following purposes.
 #
 # 1. Exclude unnecessary input methods. For example, we don't need
 #    "ja:anthy", and "zh:pinyin" engines in ibus-m17n since we have better
 #    alternatives outside of ibus-m17n. Excluding these input methods from
 #    the IBus engine XML files, such as /usr/share/ibus/component/m17n.xml,
 #    makes the startup time of the IBus daemon faster. This filtering is
 #    done using a python script at build time of ibus-m17n.
 #    See crosbug.com/4161 for details.
@@ skipping 38 matching lines @@
 #   and update the following files by running this script.
 #
 #    * chrome/app/generated_resources.grd
 #    * chrome/browser/resources/chromeos/keyboard_overlay_data.js
 #    * chrome/browser/ui/webui/chromeos/keyboard_overlay_ui.cc
 #
 #   If you add an XKB layout which depends on X11's Mod3Mask (e.g. Germany Neo2
 #   XKB layout), you should also update IsMod3UsedByCurrentInputMethod() method
 #   in chrome/browser/ui/ash/event_rewriter.cc. Otherwise, Mod3Mask might be
 #   removed unexpectedly by the rewriter.
+#
+#   If you add a new language such that all its layouts can be used at
+#   signin screen (e.g. it is "Full Latin Keyboard Language" therefore allowing
+#   input of gmail password), you should also update
+#   kFullLatinKeyboardLanguageList[] in chrome/browser/chromeos/input_method/
+#   input_method_manager_impl.cc .
+#
+#   If you add a new keyboard layout for existing language, please ensure
+#   that its "Full Latin Keyboard Language" property is not changed by new
+#   layout. If it's changed, please also update kFullLatinKeyboardLanguageList[]
+#   or change algoritm to check "this input method can be used at login screen".
 
 # U.S. English
 xkb:us::eng     us      en-US
 xkb:us:intl:eng us(intl)        en-US
 xkb:us:altgr-intl:eng   us(altgr-intl)  en-US
 xkb:us:dvorak:eng       us(dvorak)      en-US
 xkb:us:colemak:eng      us(colemak)     en-US
 english-m       us      en-US
 # U.S. English entiries have to be above the Dutch entry so that xkb:us:intl:eng
 # will be selected as the default keyboard when the UI language is set to Dutch.
@@ skipping 63 matching lines @@
 xkb:si::slv     si      sl
 xkb:rs::srp     rs      sr
 xkb:tr::tur     tr      tr
 xkb:ua::ukr     ua      uk
 xkb:by::bel     by      be
 xkb:am:phonetic:arm     am      hy
 xkb:ge::geo     ge      ka
 xkb:mn::mon     mn      mn
 # TODO(yusukes): Support xkb:latam:deadtilde:spa and/or xkb:latam:nodeadkeys:spa
 # if necessary.