Make HLSL shaders use only one main function Instead of having separate main() and gl_main() functions in HLSL shaders, add initializing outputs and inputs directly to the main function that's in the AST. This works around some HLSL bugs and should not introduce name conflicts inside main() since all the user-defined variables are prefixed. BUG=angleproject:2325 TEST=angle_end2end_tests Change-Id: I5b000c96aac8f321cefe50b6a893008498eac0d5 Reviewed-on: https://chromium-review.googlesource.com/1146647 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>