Fix DWrite axis design parameters.

DWrite makes up a bunch of axes that don't exist, so non-variable axes
are ignored. However, the actual index of the non-variable axes was not
being updated. Update it.

Bug: skia:10928
Change-Id: Iedce5d0dd58f447821b403c38f033d214b457e9f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/338602
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
3 files changed