Fix blackened background screen

Commit ag/544274 was a hack suggested by someone on the Window Manager
team to work around one of their minor issues. Its use in QuickContacts
contains a flaw. Even without this flaw, I'm still nervous about
using this code.

I can no longer reproduce b/17388576. So we may as well revert
this CL and fix b/17428798.

this reverts 2e6387f0
Bug: 17428798
Change-Id: I3c4268cfd6a8a616c3179811b933b9f42f7e3867