Delegate extensions to the right implementation based on client version. BUG=18110152 Change-Id: I3e7ccef4b466e3980210ce931ae9c1f0ff411a5b Reviewed-on: https://swiftshader-review.googlesource.com/1272 Reviewed-by: Nicolas Capens <nicolascapens@google.com> Tested-by: Nicolas Capens <nicolascapens@google.com>