Assert that SkPath is always internally consistent

Follow-on to https://skia-review.googlesource.com/c/skia/+/342616

Assuming this survives, we can probably simplify other code in SkPath
(e.g. Iterators) that today worry about consing up moves after close.

Change-Id: I913d6be9c20547267230c287d394fd300b985d31
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/342619
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
3 files changed