remove final SkTypes dependencies in SkArenaAlloc

Change-Id: I09ab433fecdba01f8e652816be08817da68eea56
Reviewed-on: https://skia-review.googlesource.com/132926
Commit-Queue: Hal Canary <halcanary@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
2 files changed