Only redraw in descriptionview/labelview if necessary

No need to drop the values and rebuild the input if nothing changed.
This saves us some redraws.

As a side effect this fixes a bug in IE11 where every redraw triggered
an 'input' event (which triggered eachchange, which then triggered a
redraw again).
That led to a redraw loop (thus the browser froze).

Bug: 71665
Change-Id: I6933efea4c622a60d47fa413233f12ac618b0f76
Merge "Only redraw in descriptionview/labelview if necessary"