Migrate prefs downloads path to MyFiles

* Added MigrateFromDownloadsToMyFiles migration during prefs init.

Bug: 911946
Change-Id: I7723226d5d759e2e2b9f4f091571ec6f92f66be0
Reviewed-on: https://chromium-review.googlesource.com/c/1367075
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615034}
1 file changed