Remove usage of BrowserThread::FILE in remaining files in value_store

Bug: 689520
Change-Id: Ib00b91bb131245b0e239eb26b5dd82d894e022ea
Reviewed-on: https://chromium-review.googlesource.com/590098
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490423}
3 files changed