lib/Ext/Container.js
function(masked) {
        var isVisible = true,
            currentMask;

        if (masked === false) {
            masked = true;
            isVisible = false;
        }

        currentMask = Ext.factory(masked, Ext.Mask, this.getMasked());

        if (currentMask) {
            this.add(currentMask);
            currentMask.setHidden(!isVisible);
        }

        return currentMask;
    }
function(masked) {
        var isVisible = true,
            currentMask;

        if (masked === false) {
            masked = true;
            isVisible = false;
        }

        currentMask = Ext.factory(masked, Ext.Mask, this.getMasked());

        if (currentMask) {
            this.add(currentMask);
            currentMask.setHidden(!isVisible);
        }

        return currentMask;
    }
Changes the {@link #masked} configuration when its setter is called, which will convert the value
into a proper object/instance of {@link Ext.Mask}/{@link Ext.LoadMask}. If a mask already exists,
it will use that instead.
@param {Boolean/Object/Ext.Mask/Ext.LoadMask} masked
@return {Object}