Replace the now deprecated findDOMNode with refs

[L3P3]

In strict mode, I get a bunch of warnings in the log:
Warning: findDOMNode is deprecated in StrictMode. findDOMNode was passed an instance of ExtTitlebar which is inside StrictMode. Instead, add a ref directly to the element you want to reference. Learn more about using refs safely here: https://fb.me/react-strict-mode-find-node
In near future, it will be gone so it needs to replaced.

This evil method is used twice inside reactize.js. I don't know why you used it there instead of passing a ref down the tree but it should defentily replaced by something non-deprecated.
I could try to fix it by myself but if I don't get anything for it, there is no point in doing that.
Thanks in advance!

[mobtex]

Sencha, when will this error be resolved?

This is annoying.