Port SkLazyFnPtr users to SkOncePtr.

First baby step on road to replacing SkLazyFnPtr, SkLazyPtr, and SkOnce.

One of those very unusual times you get to use a function type,
not a function pointer type!

BUG=skia:

Review URL: https://codereview.chromium.org/1317263007
2 files changed