function getLayoutIdxForSlide(slideNumber) {
		var layoutName = gObjPptx.slides[slideNumber - 1].layout;
		var layoutIdx = -1;

		for (var i=0; i<gObjPptx.slideLayouts.length; i++) {
			if (gObjPptx.slideLayouts[i].name === layoutName) {
				return (i + 1);
			}
		}

		// IMPORTANT: Return 1 (for `slideLayout1.xml`) when no def is found
		// So all objects are in Layout1 and every slide that references it uses this layout.
		return 1;
	}
For the passed slide number, resolves name of a layout that is used for.
@param {Number} slideNumber
@return {Number} slide number