Improve CPU and GPU usage for Mobile

1. A concise explanation of the problem you're experiencing.

   Cesium consumes CPU and GPU have all the time.After rendering ,the browser keeps occupying CPU all the time. For example, we try to load some buildings from a Json-file,when all objects have been rendered. Chrome browser will keep consuming 4% of CPU,which will drains much power. Is there some invisible rendering going on, or is cesium's listening thread occupying the CPU?

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

We need to use map on mobile devices.which can not be Charged all the time.

4. The Cesium version you're using, your operating system and browser.

The version is 1.52. Windows 10 Enterprise Edition(64bit) with Chrome.

I think here you can find some useful tips:

https://cesium.com/blog/2018/01/24/cesium-scene-rendering-performance/