This avoids having to store the type as a member field.

Bug swiftshader:12

Change-Id: I53ea4869a5b590027217d1e9cc015c0502ab530f
Reviewed-on: https://swiftshader-review.googlesource.com/7361Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>