Apologies - I submitted this prematurely before filling in the last two blocks.
I can't seem to update it myself, so here is the updated version:

Chrome Version       : 51.0.2704.84 (Official Build) m (64-bit)
URLs (if applicable) : N/A - example attached
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
     Safari: 
    Firefox: OK 46.0.1
         IE: OK IE11

What steps will reproduce the problem?
(1) Render a populated contenteditable div to screen with both CSS display set to 'inline-block' and overflow-y set to 'auto'
(2) Click into the text
(3) Hit the enter or backspace keys

What is the expected result?
A new line is either added or a line is removed, depending on the key press. The div remains in the same location on screen

What happens instead?
A new line is either added or a line is removed, depending on the key press.
The div jumps down or up the screen

Able to reproduce the issue on win8.1, mac and linux chrome version 51.0.2704.84  and canary - The div jumps down or up the screen depending on the key pressed

This is working fine in firefox browser

This is a non regression issue existing since M30 30.0.1554.0  builds to latest canary

Confirming the issue for more inputs on this

Moving this nonessential bug to the next milestone.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot