Share a single TOperator enum among all constructor AST nodes The code is a lot simpler when the type information is only carried in the TType of the node, instead of being partially duplicated in the enum value. BUG=angleproject:1490 TEST=angle_unittests Change-Id: I956376225ec01e469c7afb7378fa48cc097c0cea Reviewed-on: https://chromium-review.googlesource.com/498768 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>