add some debugging to SkNVRefCnt

BUG=skia:

Review URL: https://codereview.chromium.org/745383003
Revert "Use scratch keys for stencil buffers."

This reverts commit 91175f19664a62851da4ca4e0984a7c7c45b258f.

Revert "Cleanup res cache bench and split out into a unit test."

This reverts commit 4e4303f002c5958c6c958e7ba8e49b24c25f0b22.

Revert "rebaselines"

This reverts commit 65ba7b57759bfca60b24bc34dc46fc8caaf146f0.

TBR=tomhudson@google.com

Review URL: https://codereview.chromium.org/752233002
Add nanobench stats scripts to Skia repo.

These are the scripts I've been homegrowing for measuring perf impact.  I think we found them useful today as a way of sifting through the noise.

BUG=skia:

Review URL: https://codereview.chromium.org/703713002
make SkRefCnt::getRefCnt() debug-only, remove it from SkNVRefCnt.

Only (unused) API removed.
TBR=reed@google.com

BUG=skia:3160

Review URL: https://codereview.chromium.org/752263002
Blink hasn't rolled yet.

BUG=skia:

Review URL: https://codereview.chromium.org/754133002