Use accurate block size in SkArenaAlloc
Use accurate block size in SkArenaAlloc

Change-Id: I34c9433bb35c32bac23473e7c53d34e87b8f58f7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/601059
Commit-Queue: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>
Reviewed-by: Robert Phillips <95e8ac5504948c7bf91b22c16a8dbb7ae7c66bfd@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia