Are EXTD and INTL the only 2 languages with >2 characters?
If this is not a common pattern I'd suggest simply truncating at 2 characters without ellipsis. Effectively showing them as "EX" and "IN".
Would these enter in conflict with other languages ?

I don't know the answers to these questions. +azurewei

Re #2, I checked there's no conflict with other languages if using "EX" or "IN".

The short name is configured in field "indicator" in file google_xkb_manifest.json & google_input_tools_manifest.json. If "indicator" is not set, "language" code will be used.

While, these short names, e.g. "INTL" for US International, have been used for a long time. I wonder if we need some product perspective if changing them. 

Can we just match what the popup does?

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	0mfhnv2Hn0C.png 20.8 KB View Download

For the sake of typography balance in the shelf I'd rather go with "IN" than small "INTL". I do not think this will introduce confusion as there's no conflict with other language and as the user picked it from the IME which uses the full acronym. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b0aaaea26c58a1c0603d20a672b4a6765b9a7f99

commit b0aaaea26c58a1c0603d20a672b4a6765b9a7f99
Author: estade <estade@chromium.org>
Date: Mon Apr 17 22:55:25 2017

Chrome OS: truncate text in virtual keyboard tray item

e.g. "INTL" is displayed as "IN" instead of "IN..."

BUG= 711718 

Review-Url: https://codereview.chromium.org/2826543002
Cr-Commit-Position: refs/heads/master@{#465050}

[modify] https://crrev.com/b0aaaea26c58a1c0603d20a672b4a6765b9a7f99/ash/system/ime_menu/ime_menu_tray.cc