How to define setters for Element object in QtWebKit?

[v.martyanov]

I'm trying to define my own setter for innerHTML property, for example. JS code:
var oldDescr = Object.getOwnPropertyDescriptor(Element.prototype, "innerHTML");

	Object.defineProperty(Element.prototype, 'innerHTML',
	  {
		set: function(htmlVal)
		  {
			document.write("CATCH!");
			oldDescr.set.call(this, htmlVal);
		  }
	  });

	document.getElementById("foobar").innerHTML = "HEHE";

This code works fine in FF 39 and Chrome 43. But my new setter function is not called when I test it in qtwebkit. I tried with examples (browser/fancybrowser) from Qt 5.4. Who's wrong? How to set my setters?

[v.martyanov]

I found a bug from 2009 about the same problem: https://code.google.com/p/chromium/issues/detail?id=13175