Method when

src/common/overlay/levelRenderer/Animation.js:405–428

* @function LevelRenderer.Animation.Animator.prototype.when * @description 设置动画关键帧 * @param {number} time - 关键帧时间，单位是ms * @param {Object} props - 关键帧的属性值，key-value表示 * @returns {LevelRenderer.Animation.Animator} Animator

(time /* ms */, props)

     * @returns {LevelRenderer.Animation.Animator} Animator
     */
    when(time /* ms */, props) {
        for (var propName in props) {
            if (!this._tracks[propName]) {
                this._tracks[propName] = [];
                // If time is 0
                //  Then props is given initialize value
                // Else
                //  Initialize value from current prop value
                if (time !== 0) {
                    this._tracks[propName].push({
                        time: 0,
                        value: Animation._cloneValue(
                            this._getter(this._target, propName)
                        )
                    });
                }
            }
            this._tracks[propName].push({
                time: parseInt(time, 10),
                value: props[propName]
            });
        }
        return this;
    }


    /**