Revert "Only keep user switcher bitmaps if needed"

This reverts commit cba0faad 
with change id I416beb82156787e61ee1f59b6726fd702f135f68.

It keeps the fix preventing us from reclipping already loaded
bitmaps.

Bug: 18350670
Change-Id: I0562d38d2a6eb0b715adcd4ca77512f2cbedd320