Down arrow stops working after inserting link in Firefox

[torjusb]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
When inserting a link in Firefox, the down arrow key stops working temporarily until a new selection has been made. Up, right and left arrow keys work as expected.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem.
https://jsfiddle.net/m6z0xn4r/116/

1. Insert a few blank lines
2. Add some text to the first line, and make it a link.
3. Immediately after clicking 'Add Link', click the down arrow.

What is the expected behavior?
Cursor to move down to the next line.

Which versions of Draft.js, and which browser / OS are affected by this issue? Did this work in previous versions of Draft.js?
I'm able to reproduce this issue in Draft.JS 0.10.0 and 0.9.1 in Firefox (53.0). I've tested on Mac OS 10.12.3.

[flarnie]

Interesting - thanks for the fiddle to reproduce! It does appear to be a Firefox only bug. This is worth looking into. I'd be happy to review PRs fixing, otherwise I'll dig into it as soon as I have a chance.