[Files app] Convert ui/file_manager/base/ to arrow function

Converted using lebab with options:
$ lebab --replace ui/file_manager/base  --transform arrow

Bug: 778674
Change-Id: Iffdf7cfcc97bfd4c6342708a9176294e804235f2
Reviewed-on: https://chromium-review.googlesource.com/c/1465560
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631532}
3 files changed