在render-flow中调用eventManager._updateRenderOrder有点脏

Creator 2.x
#1

如题，本来render-flow是相对比较纯净的一个模块，最近看到引擎组为了优化EventManager 之后做了点脏活，希望可以用更好的方式解决，把引擎做到更好的模块化：

_proto._children = function (node) {
    let cullingMask = _cullingMask;
    let batcher = _batcher;

    let parentOpacity = batcher.parentOpacity;
    let opacity = (batcher.parentOpacity *= (node._opacity / 255));

    let worldTransformFlag = batcher.worldMatDirty ? WORLD_TRANSFORM : 0;
    let worldOpacityFlag = batcher.parentOpacityDirty ? COLOR : 0;
    let worldDirtyFlag = worldTransformFlag | worldOpacityFlag;

    let children = node._children;
    for (let i = 0, l = children.length; i < l; i++) {
        let c = children[i];
        _evm._updateRenderOrder(c, ++_renderQueueIndex);

        // Advance the modification of the flag to avoid node attribute modification is invalid when opacity === 0.
        c._renderFlag |= worldDirtyFlag;
        if (!c._activeInHierarchy || c._opacity === 0) continue;

        // TODO: Maybe has better way to implement cascade opacity
        let colorVal = c._color._val;
        c._color._fastSetA(c._opacity * opacity);
        flows[c._renderFlag]._func(c);
        c._color._val = colorVal;
    }

    batcher.parentOpacity = parentOpacity;

    this._next._func(node);
};
#2

:grinning: