Blacklist dftext

Distance field glyphs draw slightly differently based on where the
glyph lands in the atlas.

Change-Id: If09f95e3a707db03a658b251906c912ba504cab7
Reviewed-on: https://skia-review.googlesource.com/c/163540
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed