Have GPU and RemoteGlyphCache share mask position code

Change-Id: I0d8a969107304883ccd71c9b35ade50e3ac5d341
Reviewed-on: https://skia-review.googlesource.com/149048
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Herb Derby <herb@google.com>
7 files changed