Using input buttons can hang Chrome browser

[Mateusz Samsel]

Steps to reproduce

1. Open page with editor in Chrome Browser
2. Add checkbox
3. Click into checkbox in editor, so selection will be in input element
4. Make selection after checkbox (like you would like to write something after checkbox)
5. Browser should hang.

Alternative option:

1. Write some text in editor.
2. Add checkbox in the middle of what you wrote.
3. Start to delete text from then end.
4. When you reach the checkbox browser should stuck.

Expected result

Browser remain responding.

Actual result

It's necessary to kill process. :(

Other details (browser, OS, CKEditor version, installed plugins)

This same happen on mobile and desktop version. Test was made on Chrome 58 on MacOS.

[Jakub Ś]

DUP of #17003.