WidgetInterface - reconstructing DOMException is broken

The 'code' property is not defined in TypeError.
Therefore accessing descriptor for non existing property causes problems.

Origin of problem:
Current way of receiving native DOMException is not working.
Instead of DOMException, TypeError is received.

BUG=XWALK-2776
Merge pull request #2539 from tiwanek/XWALK-2776

WidgetInterface - reconstructing DOMException is broken