DefaultFactory 定义在 SurfaceFlingerDefaultFactory.h 中。实现都非常简单。例如 createBufferQueueLayer() 实现是调用 BufferQueueLayer 构造函数，createBufferQueue() 实现是调用 BufferQueue::createBufferQueue()。

sp<BufferQueueLayer> DefaultFactory::createBufferQueueLayer(const LayerCreationArgs& args) {
    return new BufferQueueLayer(args);
}

void DefaultFactory::createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
                                       sp<IGraphicBufferConsumer>* outConsumer,
                                       bool consumerIsSurfaceFlinger) {
    BufferQueue::createBufferQueue(outProducer, outConsumer, consumerIsSurfaceFlinger);
}

sp<IGraphicBufferProducer> DefaultFactory::createMonitoredProducer(
        const sp<IGraphicBufferProducer>& producer, const sp<SurfaceFlinger>& flinger,
        const wp<Layer>& layer) {
    return new MonitoredProducer(producer, flinger, layer);
}