Remove SkSmallAllocator.

TBR=mtklein@google.com

Change-Id: I375af12c5de4397a682c1946404282da95ad42ec
Reviewed-on: https://skia-review.googlesource.com/8392
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Herb Derby <herb@google.com>
7 files changed