inline SkArenaAlloc::allocObject()

Call overhead does appear to be showing up on our profiles.

Change-Id: If3875a8972769f45282e0eb1d4aef6324cd56878
Reviewed-on: https://skia-review.googlesource.com/17833
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
2 files changed