Add test for D3D11 nested floor() bug The test fails on D3D11, which seems to ignore floor() calls if they're nested in a particular way with magic multipliers inside. BUG=chromium:838885 TEST=angle_end2end_tests Change-Id: I2c8749defa923553bfee69149da15f8e4ddf5096 Reviewed-on: https://chromium-review.googlesource.com/1041959 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>