GitLab

The file thread is no longer used. TaskScheduler should be used for
all file operations.

Bug: 
Change-Id: Iba07dc70a721c2c84cdb7ac00b7d4be057ae83aa
Reviewed-on: https://chromium-review.googlesource.com/660599Reviewed-by: Gene Gutnik <gene@chromium.org>
Commit-Queue: Francois Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501273}