gralloc: Add asynchronous lock/unlock API

The existing API exposed to clients for software lock/unlock forces the gralloc
implementation to complete these operations synchronously. This change adds new
entry points for lock/unlock functionality that is suited for use with Android's
explicit synchronisation concept. This provides scope for the gralloc module
to internally optimise the work it must do for lock/unlock and to hide this cost
from the client.

Change-Id: If4b1bb5490ab2b20d796214a7da8a96427cfe52d
1 file changed