The foreground processes will always get scheduled ahead of the background process, and be able steal its evicted pages from the Standby list, thus reducing their own need for paging to external media.

If all you care about is getting your updater to complete quicker, you should not be using the background mode, but ideally the Chrome updater would run in the background without affecting the performance of the foreground applications. Allowing for working set peaks, no matter how short, will fail to achieve that on systems experiencing memory pressure.