Add visible check on textarea on resize event and stop propagation

[jlowcs]

Had some trouble in Chrome when forceApply=true : resize event in triggered on textarea when its parent is hidden, which has every placeholder being repositionned (which can be seen by the user).

This fix checks if the textarea is visible before repositionning the placeholder. It also stops the propagation on textarea resize.

[ginader]

thanks for that @jlowcs :-)