Refactor translator construction The patch adds functionality to determine whether compiler output belongs to the ESSL, GLSL, HLSL or Vulkan output family. The new functions can be now used in other parts of the compiler in which code paths are selected based on the compiler output. BUG=angleproject:2062 TEST=angle_unittests Change-Id: I45ccf63f0a756c60df47a679c2da9f60856d5918 Reviewed-on: https://chromium-review.googlesource.com/558990 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>