Replace GrTHash with SkTDynamicHash

Mike: SkTDynamicHash changes
Brian: Ganesh changes

This removes three instances of GrTHash leaving the ones in GrTextStrike.h

R=mtklein@google.com, bsalomon@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/402693003
9 files changed