remove legacy drawstring

Bug: skia:
Change-Id: Id3491dbc6cee3e5d06981284535a04639182e9dd
Reviewed-on: https://skia-review.googlesource.com/c/182450
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed