Dump out path-mask generation and caching stats

These stats would've helped block https://skia-review.googlesource.com/c/skia/+/286902 (Add path bounds to SW path mask key) from landing.

Change-Id: I684f39de53fb2678c7a679e4e4aafdbb39a154ca
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/287499
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
11 files changed