Revert "[legacy sf flag] - Remove legacyFrontEndEnabled"

This reverts commit 11e197a2e438f0ea16066ff6118294a5fa3b26a3.

Reason for revert: caused regression in arc.PlayStore.betty_vm see http://b/337352234

Change-Id: I9ba883f0190b82ac1e00ed47ace8bec4e8a46fa6
5 files changed