Explicitly expose supported GMB formats in gpu::Capabilities

Instead of trying to derive GMB support from extension bits, explicitly
expose the set of supported GMB formats.
A compact representation (bitfield) is introduced to easily and cheaply
pass the set around.
In later CLs this will be used in other contexts (shared images).

Bug: 870116
Change-Id: I393b98dda067dba0c41d74e6de390ae478f50520
Reviewed-on: https://chromium-review.googlesource.com/c/1313549
Commit-Queue: Antoine Labour <piman@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605624}
10 files changed