Move adding a glyph to a subRun from Run to SubRun

Change-Id: I61e7c42f27480b6d5923073a5f7eb5a27726a4b2
Reviewed-on: https://skia-review.googlesource.com/c/170424
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed