Remove posText system from GrTextContext

Remove the drawPosText code stack, and all supporting code.

Change-Id: Ie6ee64d012d390911faeb3c486d66cac40497744
Reviewed-on: https://skia-review.googlesource.com/145533
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
6 files changed