Performs one layout cycle by calling each layout in the layout queue.
@return {Boolean} True if some progress was made, false if not.
@protected
function () {
        var me = this,
            layouts = me.layoutQueue.clear(),
            length = layouts.length,
            i;

        ++me.cycleCount;

        // This value is incremented by ContextItem#setProp whenever new values are set
        // (thereby detecting forward progress):
        me.progressCount = 0;

        for (i = 0; i < length; ++i) {
            me.runLayout(me.currentLayout = layouts[i]);
        }

        me.currentLayout = null;

        return me.progressCount > 0;
    }