Added missing header

Change-Id: Ibc44597e6c4c07686dfc775cff9877e417c66542
Reviewed-on: https://swiftshader-review.googlesource.com/2665
Tested-by: Greg Hartman <ghartman@google.com>
Reviewed-by: Greg Hartman <ghartman@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>