图形驱动程序排队的最大帧数。
图形驱动程序可以对要渲染的帧进行队列处理。当 CPU 的工作明显少于显卡时，
该队列可能会变得相当大。在这种情况下，
用户的输入将“落后于”屏幕上的内容。
Use QualitySettings.maxQueuedFrames to limit maximum number of frames that are queued. On PC, the default value is 2,
which strikes the best balance between frame latency and framerate.
Note that you can reduce input latency by using a smaller maxQueuedFrames because the CPU will be waiting until the graphics card finishes rendering previous frames. The downside of this however, is that it can result in a lower framerate.
Currently maxQueuedFrames is implemented in Direct3D 9, Direct3D 11, and NVN graphics APIs; it will be ignored by other graphics API.