Revert "libgui: Bring back support for mHeap-based screenshots"

This reverts commit e5dfc8f220eed32fffc0b26b6aca55444f4f7b8e.

This patch was obviously horribly mismerged, as it brings in a pile
of non-ifdefed code when implementing a patch that was previously
100% ifdefed.

It's also causing crashes on i9100g

Change-Id: Ia1ade0b76269204fab6660a4e1ad26853a043e60