Update media galleries file scanning to not use FILE thread.

Bug: 689520
Change-Id: Ifd7dacab92f3550cc3bd1c0d94716fd282fdf3be
Reviewed-on: https://chromium-review.googlesource.com/644589
Commit-Queue: Ben Wells <benwells@chromium.org>
Reviewed-by: Francois Doray <fdoray@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499937}
6 files changed