This class will manage GPU binary programs in memory. It will be
owned by the Display, and shared between Contexts. Currently this
CL just refactors the Program binary saving and loading into static
members of this new class.

BUG=angleproject:1897

Change-Id: I34f5afb2c02416f6fd80dd65ba3827a8637ce190
Reviewed-on: https://chromium-review.googlesource.com/522873
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>