Move mask rendering to its own routine

This will make it so I can move the routine to SkGlyphRun.cpp
to use all the shared code.

Change-Id: If8107cfb523e60b3f1120d8722666e7c2ade639d
Reviewed-on: https://skia-review.googlesource.com/149044
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
1 file changed