Some NVIDIA D3D11 drivers are buggy and interprets the level passed to
GetDimensions as being relative to 0, rather than the SRV's MostDetailedMip.
A test is added which reads from non-zero base level integer texture. When the
workaround is not being used, reads outside the first quadrant return black.

Bug: chromium:679639
Change-Id: I5282a1ba207b2d553d1836f9460ec09cb5590ea6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1591594
Commit-Queue: Kimmo Kinnunen FI <kkinnunen@nvidia.com>
Reviewed-by: Kimmo Kinnunen FI <kkinnunen@nvidia.com>