Revert "Revert "remove (empty) SkXfermode.h""

This reverts commit c5d0147717e50acba106b76c6c345192274ddc06.

g3 is updated to allow this to land

BUG=skia:

Change-Id: I5f4b06c2dc77dfa66d9b32348375151177511a65
Reviewed-on: https://skia-review.googlesource.com/5406
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed