Remove indexes from Geometry in the text op

Using indexes to name subruns seems overly complex. Just use pointers.

Change-Id: Ia02aed6a07e6bf91b70e42c45a0c5f6f903fa815
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/254796
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
6 files changed