There is currently a functional, but incomplete, alternate implementation of the gpu-host in services/ui/gpu_host/ [1]. Once the complete implementation in content is moved into components/viz/host [2], these are no longer needed, and should be removed.

[1] https://cs.chromium.org/chromium/src/services/ui/gpu_host/
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=709332