Handle negative float to uint conversion robustly Converting a negative float to uint is undefined in the GLSL ES 3.00.6 spec. However, it improves portability if we don't trigger undefined results in C++ in this case. To do this, we cast negative floats first to signed integer before casting them to unsigned integer. We also issue a warning about an undefined conversion in case a negative float was converted to uint. BUG=chromium:835868 TEST=angle_unittests Change-Id: I9835a739ec80699d420a4f91a3bfa112c9a13604 Reviewed-on: https://chromium-review.googlesource.com/1026681 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>