Add a FixedVector class to have "variable" size vectors on the stack. Wraps a std::array and a size parameter to give the std::vector interface without making allocations. BUG=angleproject:2435 Change-Id: I7df0be1310446a2f163766149bf631a8692be9ad Reviewed-on: https://chromium-review.googlesource.com/981267 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>