Split ternary node class from TIntermSelection Ternary operator nodes are typed parts of expressions, they always have two children and the children are also guaranteed to be TIntermTyped. "If" selection nodes can't be a part of an expression, they can have either one or two children and the children are code blocks. Due to all of these differences it makes sense to store these using two different AST node classes. BUG=angleproject:1490 TEST=angle_unittests Change-Id: I913ab1d806e3cdb5c21106f078cc9c0b6c72ac54 Reviewed-on: https://chromium-review.googlesource.com/384512 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org>