getContainerDimension = function(oControl, sDim){
		var oProp = getPropertyInfo(oControl, sDim);
		if (oProp) {
			var val = oControl[oProp._sGetter]();
			if (val && val.endsWith("%")) {
				return val;
			}
		}
		return null;
	}
Returns the value width or height property (depending of <code>sDim</code>) of the given
control if the width or height is specified in %.

@private