Keep TIntermSymbol nodes consistent in PruneNoOps Create new TVariables to change struct declaration qualifiers in PruneNoOps so that the node doesn't end up with an inconsistent qualifier from the variable. BUG=angleproject:2267 TEST=angle_unittests Change-Id: I7f6cd557eb3e46f4ead4ffbe37d8960ff7776d10 Reviewed-on: https://chromium-review.googlesource.com/850673 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>