undef guard for bitmap shader

Bug: skia:8937
Change-Id: I25a70f4700f2809477d31e2bf3632fa948d0bc54
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206689
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
2 files changed