Optimize fs_watcher to use less RAM by doing less work (#39602)

mac_watcher already does this so it would make more sense to also do
this on Windows and it saves ~500-600mb of ram on the chromium project.

This does not improve memory usage on linux because inotify cannot do
recursive directory monitoring

Release Notes:

- N/A
6da5945cd2localcc committed on 10/6/2025, 4:24:28 PM· committed by GitHubparent354cc65
1 file changedLine totals unavailable