LinkedList = function () {

	        /**
	         * @type {module:zrender/core/LRU~Entry}
	         */
	        this.head = null;

	        /**
	         * @type {module:zrender/core/LRU~Entry}
	         */
	        this.tail = null;

	        this._len = 0;
	    }
LRU Cache
@constructor
@alias module:zrender/core/LRU