[Password Manager] Set exported passwords permission to 0600 on posix

Currently, Chrome uses the user default (umask), which may be too broad
for sensitive files. We will restrict all permissions to users other than
the owner.

Bug: 921308
Change-Id: I9c03b57ae1392926a6f912372a8eae8e4c6b3cfb
Reviewed-on: https://chromium-review.googlesource.com/c/1426678
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625193}
3 files changed