Redo is broken after undoing typing with IME

[Piotrek Koszuliński]

1. Open replacebycode sample.
2. Set your system language to Japanese Hiragana.
3. Type 2-5 letters and press enter to commit composition.
4. Repeat the above few times.
5. Press CTRL+Z (not the undo button).
6. The changes were undid, but the redo button is disabled.

Reproduced on FF and Chrome. This issue is a little bit random - I think that order in which the CTRL and Z keys are released matters. In my case I was first releasing Z and then CTRL.

In ​http://dev.ckeditor.com/ticket/12391#comment:4 Artur suggested that there may be a change fired. I'm rather thinking that keyup causes the onTypingStart function to be executed.

Related issues: #12391, #12597.

[Jakub Ś]

Problem can be reproduced in FF, Webkit and Blink (IE is fine) from CKEditor 4.4.4.