remove unused colorfilter virtual asACompose

Bug: skia:
Change-Id: I1e23dbd18f7145dcaaa864f3fd7b34aea2c342a6
Reviewed-on: https://skia-review.googlesource.com/19269
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed