GitLab

Moves responsibility for validating that holding space items restored
from persistence delegate to file system delegate.
The persistence delegate just de-serializes items from the persistent
storage and adds them to the model as partially initialized items.

File system delegate handles file path validity for non-finalized items,
and removes items whose backing file path cannot be found from the
model. This results in a simpler restoration flow where file validity
checks can be unified.
This CL updates the logic for file existence verification when items
are restored from persistence to better items from mount points that
are not immediately mounted very on startup (for example drive fs).

The file system delegate will leave items whose file system URL cannot
be resolved in partially initialized state until a mount point that
parents the item is mounted.

Note that the items will not remain in partially initialized state
indefinitely - they will be cleaned up if the volume has not been
mounted soon after startup.

Renames ScopedTestDownloadsMountPoint into ScopedTestMountPoint and
makes is a bit more customizable by tests - for example, enables tests
to set up mount point state when the mount point is added to the
external mount points.

BUG=1140150

Change-Id: I924b9b932039d1f1a1498dc3ce4b73ddeac0ddbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490259Reviewed-by: Josh Nohle <nohle@chromium.org>
Reviewed-by: David Black <dmblack@google.com>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823849}