I'd suggest disabling spellcheck entirely on Jellybean instead.  Jellybean is down to a few % of our user population and Chrome is probably no more than a year or two from dropping support for it.

I already have a fix ready, I'd like to keep Jelly Bean support for now:
https://chromium-review.googlesource.com/c/chromium/src/+/636205

I did previously spend some time specifically to support pre-Lollipop versions (so Jelly Bean and KitKat; KitKat has similar user share as Nougat), but I think this the first actually Jelly Bean-specific fix we've needed so far.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c0cb3eb47653341336c350c01d239c346d9d6208

commit c0cb3eb47653341336c350c01d239c346d9d6208
Author: Ryan Landay <rlanday@chromium.org>
Date: Wed Aug 30 00:38:29 2017

Fix crash adding long word to dictionary on Android Jelly Bean

Android Jelly Bean has a bug in the "add to dictionary" intent we're using where
adding a word longer than 48 characters long will crash the whole browser. It's
not terribly difficult to hit the "add to dictionary" button on accident, so
this seems like a fairly serious crash. This CL fixes the crash by pre-trimming
the word on Jelly Bean (the code is version-gated to make it easier to remove
once we drop support for Jelly Bean).

Bug:  759119 
Change-Id: Ifce566a17e3da315a2711bd071e8c7220f897e98
Reviewed-on: https://chromium-review.googlesource.com/636205
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Ryan Landay <rlanday@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498312}
[modify] https://crrev.com/c0cb3eb47653341336c350c01d239c346d9d6208/content/public/android/java/src/org/chromium/content/browser/input/SuggestionsPopupWindow.java