Start D3D constant register allocations from 1 on NVIDIA Recent NVIDIA drivers have a bug where a specific optimized path inside the driver doesn't handle constant register 0 correctly. Work around this by starting constant register allocations from 1. This should make sure that the bug doesn't trigger if the ordering of uniforms is changed on the D3D backend. The repro case seems to require some specific driver state to be set that's used inside Chromium. Because of this we have not been able to develop a standalone test case so far. The maximum number of available uniform slots is reduced accordingly. This should not take them below required minimums in the spec. BUG=angleproject:2294 TEST=WebGL tests on passthrough command buffer, angle_end2end_tests --gtest_filter=*GLSLTest*Uniform* Change-Id: I92fff71efe5432ea7f15a7e90d497492514c65dc Reviewed-on: https://chromium-review.googlesource.com/847481 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>