Databases and SharedPreferences often involve multiple files under
the hood, so developers wanting to migrate them between different
storage contexts should ask us to make sure all relevant files are
migrated correctly.
This makes a best-effort attempt to recover from battery pulls
during migration, while still trying to alert developers to
conflicting files.
Bug: 26668510, 25860525
Change-Id: I9ffa3e8cb6191dfd4237b9466a081d6d77df3ba0
35871f2c2b