Repro:
* Delete files from Safe Browsing/ dir, and chmod a-w it so it can't be written to.
* Wait for update


Looks like it also shouldn't move the new (bad) file to replace the old one, since there could be an old one that's at least not corrupt.

https://cs.chromium.org/chromium/src/components/safe_browsing_db/v4_store.cc?type=cs&q=v4_store.cc:748&sq=package:chromium&l=741