BUG=angle:914

TEST=dEQP tests
Tests passing 100% because of this change:
  dEQP-GLES3.functional.shaders.operator.common_functions.min.*
  dEQP-GLES3.functional.shaders.operator.common_functions.max.*
  dEQP-GLES3.functional.shaders.operator.common_functions.clamp.*
Reduced number of errors in tests:
  EQP-GLES3.functional.shaders.constant_expressions.builtin_functions.common.*
  These tests are not yet passing because of constant expressions
  bug (angle bug:913)

Change-Id: Ibccee47ed78e994e40a0effe9afa9cf9692492b0
Reviewed-on: https://chromium-review.googlesource.com/250330Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Nicolas Capens <capn@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>