invalidate pathref bounds when we attach an editor

It's possible to change path bounds by changing path points using
SkPath::setLastPt(), but we don't invalidate the bounds when we do.

Seems like the best thing to do is to invalidate the bounds when
we attach an editor, the same way we invalidate the gen ID.

Bug: oss-fuzz:10488, oss-fuzz:10698
Change-Id: Idd04d37f9e39979aac135d675aa4e5949c55a453
Reviewed-on: https://skia-review.googlesource.com/156700
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>

src/core/SkPathRef.cpp

@@ -40,6 +40,7 @@ SkPathRef::Editor::Editor(sk_sp<SkPathRef>* pathRef,
     fPathRef = pathRef->get();
     fPathRef->callGenIDChangeListeners();
     fPathRef->fGenerationID = 0;
+    fPathRef->fBoundsIsDirty = true;
     SkDEBUGCODE(sk_atomic_inc(&fPathRef->fEditorsAttached);)
 }