SafeMakedirsNonRoot tries hard to create non-root directories, even if the target directory, or a path prefix thereof is owned by root.
eg: https://chromium-review.googlesource.com/#/c/404152/

We have had to go replace various uses of SafeMakedirs with the *NonRoot variant to allow fixing incorrectly root-owned paths.
eg:
https://chromium-review.googlesource.com/#/c/404153/
https://chromium-review.googlesource.com/#/c/410285/

This is a cleanup bug to audit all uses of SafeMakedirs and replace them with *NonRoot wherever the intention is to make non-root directories only.