Don't switch to the default display root if the current entry is fake.

If a FakeItem is the current entry and a volume is mounted or unmounted,
Files app switches to the default display root since the FakeItem
doesn't have a VolumeInfo. Omit switching if the current root is not a
native entry.

Bug: 900870
Change-Id: I943959112135ceb5752207f87e6810a4ec60ae0f
Reviewed-on: https://chromium-review.googlesource.com/c/1312148
Commit-Queue: Sam McNally <sammc@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605221}
3 files changed