a few text blob and text op cleanups

Change-Id: I2dd7cacc19232c0ff9d890c613fe6cc2346e8553
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/371142
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed