vboot_display: Record screen change even on error
vboot_display: Record screen change even on error

VbExDisplayScreen/Menu() can fail for many reasons... most often because
some asset that was part of the intended screen couldn't be found. Most
of the errors are permanent and will not get better by trying again.

The respective vboot wrapper functions track the last screen change that
was requested so that we don't keep drawing the same screen over and
over again for every keyboard poll. The current code does not update
this tracking when there was an error during drawing, but the benefit of
this is questionable... those errors usually mean that some part wasn't
drawn correctly, but they don't mean "please keep trying". This problem
is currently worked around in depthcharge by just always passing
VBERROR_SUCCESS even if the underlying screen drawing calls failed, but
it seems cleaner not to hide this error from vboot and instead make
vboot deal with it better.

BRANCH=None
BUG=None
TEST=Navigated through some menus both with and without bitmaps in CBFS.

Change-Id: I3d86a5150fddce9fab18189b2b706960d429b2b7
Signed-off-by: Julius Werner <4d12f06cff3725783b352157673a720bc67c4afe@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1497037
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>
Reviewed-by: Mathew King <5f5c121488ff77c128d954b29ebebffa1909e0f6@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot