This change adds a stub cache implementation that gets passed to the
underlying EGL implementation at initialization time.
Change-Id: I14437c5b6f91b7a34a19bb02ad802e6e54f88d2a
as specified by the EGL specification, terminated objects's
handles become invalid, the objects themselves are destroyed
when they're not current to some thread.
Change-Id: Id3a4a5736a5bbc3926a9ae8385d43772edb88eeb