Generate performance warnings in HLSL translation Generate performance warnings for some code that undergoes heavy emulation when translated to HLSL: 1. Dynamic indexing of vectors and matrices. 2. Non-empty fall-through cases in switch/case. The warnings are generated only when code is translated to HLSL. Generating them in the parsing stage would add too much maintenance burden. Improves switch statement fall-through handling in cases where an empty fall-through case follows a non-empty one so that extra performance warnings are not generated. BUG=angleproject:1116 Change-Id: I7c85d78fe7c4f8e6042bda72ceaaf6e37dadfe6c Reviewed-on: https://chromium-review.googlesource.com/732986 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org>