Add missing virtual destructor on TIntermAggregateBase BUG=angleproject:1490 TEST=build on Linux GCC Change-Id: I64f53d636d4acee0469b6e9ba1201322087d5f65 Reviewed-on: https://chromium-review.googlesource.com/395732 Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>