Remove ability for Release code to call getRefCnt() or getWeakRefCnt().

These getRefCnt() methods are not thread safe, so Skia code should not
be calling them.  unique() is fine.

SkDEBUG code (SkASSERTs) can still call getRefCnt() / getWeakRefCnt().

This adds tools/RefCntIs.{h,cpp}, which lets tests make their assertions in
both debug and release modes.

BUG=skia:2726
R=senorblanco@chromium.org, mtklein@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/378643003
16 files changed