[macOS] Undo not working properly with pin

[haivp3010]

Current behavior

(as observed in the demo page http://reactdesktop.js.org/docs/mac-os/pin)

• When performing undo on previous input, the previous box is cleared but the cursor is still kept at the current box.
  

• Undoing backspace is not working i.e. the deleted number is not restored.

Expected behavior

• Undoing inserting should restore previous position of the cursor.

• It should be possible to restore deleted number by undo operation.

[gabrielbull]

@haivp3010 You can submit a PR if you'd like this behavior to change

[haivp3010]

@gabrielbull OK I will look into it